Mermaid Melody Pichi Pichi Pitch crossover Fusion Fic side-story?

For a long while, I wanted to do the following: Attempt to implement the Mermaid Melody Pichi Pichi Pitch animé in the My Little Pony world (whether or not Equestria is its name is something else), or to be precise the main setting of Shisno Chronicles: Friendship is Magic. Already I implemented some of its main characters in the form of the P3, which I have mentioned a few times in the start of the "season 2" arc, once in "Dangers of Vengeance", a couple times in "Luna Eclipsed" in dialog and Chronicle's…costume of choice, and in the "Special 6: Chronicle's Birthday Party", where three (no, four) characters appear in pony, four more in a flashback, and two in mere dialog.

However, while I can check out the anime whenever I like, I lack the know-how regarding the entertainment industry (since in SC:FiM, they're idols like Sapphire Shores and not 'covering' as high school students like in the animé), how to implement its story without potentially breaking any future/present canon regarding merponies, seaponies or any other undersea civilizations, whether or not I can make it conceivable in the MLP world, whether or not I should go for the fantasy end with the "Merpony Duchess" deal or make it slice-of-life mundane (well, as mundane as MLP can be), and making it entertaining enough.

In the end, I decided to leave the groundwork for someone who's interested, as well as ponified (more like converted-for-MLP as I decided to make some of them other races like griffons, diamond dogs, etc.) versions of the MMPPP characters.

Format:
["P3" Character], [race] ([MMPPP character they're based on]) - [tidbits on backstory]

As for the deal regarding them being "Merpony Duchesses" that was alluded to the recounting of a concert in Baltimare where the P3 performed (and which Rarity was also a witness to), let's say their race above is what they're disguised as, and some of their history could just be cover stories.

I apologize for any spoilers for Pichi Pichi Pitch, but some of those could easily be original story.

The P3 - an idol singer group famed across Equestria's East Coast (i.e. their hometown Baltimare [just like Mystic Shield, hence why he's a fan], Manehattan, and Fillydelphia) though they're also known further west. They're also known for composing their own songs.

The Core Cast/"Face of the Band" - Even before their road to stardom, the three have been great friends, though Sealight and Sound are closer since Jasmine only joined a bit later. While they often sing together in performances, they've also done their share of solos, as well as duets with each other or with their coltfriends. Another thing they share, aside from proficiency in swimming (Sealight being the best of them), is hate for those who would mock/insult/otherwise belittle the power of love.

Sealight Glisten, earth pony (Lucia Nanami) - The somewhat naive and emotional leader of the P3. She leads because of her cuteness appeal, her charm, and her optimism. While under all that isn't a brilliant mind or (Celestia forbid) an unstable psyche, she isn't an all-out ditz like some would at first believe of her. Her motif is pink.

Sound Wave, pegasus (Hanon Hosho) - The love-struck and rather girly second of the P3. Her favorite topic is romance, she's a (positive) gossip girl, has some rudimentary training in Ponyrate for self-defense, and is a good bowler. Her motif is aqua/blue.

Jasmine Trinity, unicorn (Rina Toin) - The tomboyish yet ladylike-looking third of the P3. She's a little chilly, and is the only one among them willing to get rough in a hoof-fight. She also has a fascination for advances in technological communication and comedy routines. Her motif is green.

Merpony Melody - the P3's band. The ones who do the instruments while the P3 provides the voices. While not as prominent as the P3, they have their own fanbase, and sometimes play for other singers. (These are original characters, and I did my best to figure out what instruments were used in the MMPPP songs and made these characters via these.)

Firm Riff, earth pony - She's the lead guitarist of the Merpony Melody. She and Mild Strum are sisters.

Mild Strum, pegasus - She's the bass guitarist of the Merpony Melody. she and Firm Riff are sisters.

Soft Beat, pegasus - He's the drummer of the Merpony Melody.

Harmony Synth, unicorn - She uses an electric keyboard to fill in some of the other various instruments the Merpony Melody lacks.

Silver Strings, unicorn - Violinist and Cellist of the Merpony Melody. She also knows a spell that can make a solid duplicate of her, which she uses to fulfill both of her roles at once.

Cool Brass, earth pony - The trumpeter in the Merpony Melody, though he's also talented in other brass instruments.

Other Members of the P3

Nicole Seacrest, earth pony (Nikora Nanami) - Manager and backer of the P3 and Sealight Glisten's mentor. To keep things professional, she hides the fact that she and Sealight are siblings, she being the older one.

Pocampus, diamond dog (Hippo(campus)) - Assistant manager and (more often) bodyguard of the P3. Once when he was sick, the P3 hired Chronicle to substitute for him. He had been adopted into the 'family' after an incident when back as a filly Sealight was foalnapped by a pack of diamond dogs. The subsequent rescue mission was a success… and also ended up taking Pocampus with them. As he was the runt, the pack did not want him back, so Nicole took him in.

Southern Snow, pegasus (Karen) - Solo artist and occasional extra singer for the P3. Her initial encounters with the P3 were rather cold, and she'd rather not work with them (even leaving them to pay her sizable restaurant bill once), but her twin sister Northern Snow eventually hleped her warm up to them. On occassion, the Merpony Melody serve as her band when she sings her solos. Her motif is purple.

Northern Snow, unicorn (Noel) - Duet singer with Southern Snow and and occasional extra singer for the P3. Outside the spotlight, she's a bookworm focused on the occult and magical theory, which she does her best to hide. She was once blackmailed by Abysmal Star to be in his service before being…helped out by the P3, thus earning her and Southern Snow's trust. Her motif is deep blue/indigo.

Coconut Cream, earth pony (Coco) - Extra singer for the P3. Like Northern Snow, she was under Abysmal Star's service via…a huge debt to pay him before the P3 helped her out of her jam. She and the other singers of P3 (with the exception of Sealight) are pretty good at volleyball. Her motif is yellow.

Syrene, griffon (Sara) - Solo artist and occasional extra singer for the P3. Prior to joining the group, she was under Abysmal Star's service because her daughter was used as ransom, though that wasn't the only incentive Syrene had to stay with him. Even after the rescue though, she still has feelings for him. Her motif was black, but shifted to orange.

Siebel, griffon (Seira) - Syrene's daughter. She was once kidnapped by "Assemil-8" for his plans, but she was eventually rescued. She's training to become an idol singer just like her mother and P3.

Friends of the P3

Tidal Star, pegasus (Kaito Domoto) - ace surfer, beach heartthrob, and coltfriend of Sealight Glisten. Back when he was just a colt, during a storm that sank the ship he and his parents were in, he fell off it and into the depths. Reportedly, Sealight was the one who saved him and brought him to shore. In occasions, he sings with her in duets.

Cadent Note, earth pony (Taro Mitsuki) - musical teacher of the P3 and sometimes serves as the pianist for slow and soft songs. He was the object of Sound Wave's affections before he eventually convinced her to move on.

Racer Hoof, earth pony (Masahiro Hamasaki) - a stallion with a martial arts career and a need for speed, taking daily gallops around the shoreline of Baltimare. His…involvement with the P3 began when he saw Jasmine Trinity about to dive into the sea from a 10-foot tall cliffside. Incorrectly thinking she was about to commit suicide, he pulled her away, she got cross and left, he tried to apologize to her, her friends were excited that she has a coltfriend now, one thing led to another, and they eventually became for real, even singing in duets.

Black Slate, unicorn (Nagisa Shirai) - A young teenage colt who has become a fan of P3 and leads one of its fanclubs that focus on particular members, his being the ones for Sound Wave. But he doesn't just stick to adoration; he also takes the time to assist Sound herself without coming off as a stalker and has unknowingly became her "new flame", as much as she'd deny it. At the very least, they're close enough that she'd pick him as her duet partner disguised as appreciations for his fanclub's dedication.

Alicia, unicorn (Mikaru Amagi) - Sealight Glisten's love rival for Tidal Star.

Silver Baton, unicorn (Rihito Amagi) - Alicia's older brother who works as a conductor for an orchestra.

Antagonists of the P3

Abysmal Star, unicorn (Gaito) - Manager of a number of singing idol groups, among them the Black Beauty Sisters, and bastard brother of Tidal Star (or is Tidal Star the bastard brother, no one's really sure). He aspires to take every celebrity possible into his fold, and despises Sapphire Shores for remaining out of his reach. Because bribes sometimes don't work, he often uses underhoofed methods in an attempt to force the P3 into his management, having a stalker-like fascination for the singer trio, as well as the ones they have 'rescued' from his hold.

Aqua Scale, unicorn (Izuru) - The de facto leader of the Dark Lovers gang, a quartet of mercenaries who are regularly hired by Abysmal Star to strongarm aspiring stars under his wing (so to speak, since he's not a pegasus), defend his assets, and sometimes serve as his harem. Her signature spell is the ability to call forth a sea serpent out of water to intimidate, attack, drown, and transport her team across the waters.

Dual Twister, pegasus (Eriru) - A member of the Dark Lovers gang. She has a personality disorder, changing between perky and nasty but is dangerous either way. She has mastered a pegasus spell that creates a vortex of wind around herself while she spins, enabling her to do a lot of damage on a foe or blow away whoever's in her path.

Sleet Heart, unicorn (Maria) - A member of the Dark Lovers gang. She's cold-hearted, really loves mocking the love of others, and is skilled in the art of cryokinesis, down to conjuring small blizzards. She's considered the most dangerous out of the four.

Short Pitch, earth pony (Yuri) - The child prodigy of the Dark Lovers gang. She has the uncanny ability to entrance or torment others with music from a grand piano. While it would be normally cumbersome, Aqua Scale's conjured sea serpent can carry it without ruining it.

Maroon Shade and Navy Shade, earth ponies (Sheshe and Mimi) - an earth pony duo and rival singer group called the Black Beauty Sisters. For some reason, the P3 (excluding the Merpony Melody) experience pain when they hear their songs. One of their most scandalous secrets is that not only are they lesbians, their relationship is incestuous (i.e. they love each other romantically).

"Assemil-8", griffon (Mikeru) - Manager of a number of singing idols. An adept in runes, he desires a…'rare component' to stave off death from a curse that was inflicted on his family. To this end, he abducts young girls of all races to harvest this component, but what he requires most is from merponies, which he believes the P3 are. Still, he's knowledgeable enough in the art of being discreet to avoid evidence pointing to him.

Charming Soul, thestral (Lady Bat) - A cross-dressing idol singer under "Assemil-8"'s wing. He had a mare-like face and voice, the latter of which can hypnotize and put to slumber those who listen when he chooses to use its power when singing. He hates garlic due to his sensitive throat.

Violet Dancer and the Pixies, earth pony w/ Glimmer wings (Lanhua) - An idol singer with a fascination for Neighpon culture, and her band of twelve fanatical foal followers (four of each race). All of them are under "Assemil-8"'s service. Violet's band play a wide variety of instruments, allowing Violet to make covers for nearly every song in existence. Her band's instruments also somehow have the ability to force listeners to dance uncontrollably, making it good for kidnapping.

Passion Burn, unicorn w/ Glimmer Wings (Alala) - A very perky idol singer who really loves her career, going as far as to pursue it above following "Assemil-8"'s directives. Her special talent is causing things to 'burn' from the inside, ranging from igniting fuel tanks to sparking passion in her fans, to causing moderate heartburn to those who listen to her songs.