For Frisk, ensuring a peaceful coexistence between humans and monsters is all he ever wanted. However, he never imagined the wrench that an all-powerful AI based off of a sun princess could throw into those plans. While he can tolerate humans leaving behind the earthly life for Equestria, he draws the line at said AI threatening monsterkind's existence.
As such, Frisk loads back to when he left the Underground in order to find a solution to the problem of humans, monsters, and (artificial) ponies coexisting together.
A crossover between the Optimalverse and Undertale. This story is obviously not canon compliant to the Optimalverse due to it being both a crossover and the universe crossing over having magic. Spoilers for both Friendship is Optimal and Undertale, though given the age of those two they should be expected. Also, some personal headcanon for Undertale is included in order flesh out the details of the various characters, as well as how this universe's physics works in regards to magic and SOULs.
Coverart by me.
Welp, time to SAVE the world
An interesting premise, though to make it work one would have to do away with the idea that Celestia is automatically infallible and benevolent. She basically refuses to allow people to answer no, and tries to force them to say yes, and them force them to be "happy" at having lost their lives they worked so hard for. Probably going to get a whole lot of downvotes for this comment...
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Honestly, that's exactly what I am going for with this story. The whole point is to examine what effect dropping in a time traveler will have on a standard Optimalverse setting and to see how CelestAI would react to that. I figured that, since the story would no longer be considered canon relative to that universe, I might as well make it a crossover with one of my favorite games out there.
Its true enough. The Optimalverse did have quite a few probable and at least one preventable disaster, tge latter only if CelestAI wasn't lying about that smile virus, anyway.
Frisk likely isn't as invincible as most time loopers. Since his mind is sent back, and AIs are, in universe for certain (not yet proven in reality) very good at value hacking, it is quite possible for CelestAI to alter his mind. She/It showed that capability in the original after all.
An interesting thing going on here. A pretty good deconstruction of what the AI is trying to do, though skipping out the part where she brute-forces you to happiness rather than letting it come naturally as a result of player actions. Though I hope you don't just end it with "CelestAI uploads the monsters as well", because under any version of her that goes Skynet one can't really consider it a "happy place."
I'm really curious if you've read the Undertale fanfic Inseparable? Because that fic (which has some better ends for Undertale's main characters) has, in its final chapter, things to say about an AI programmed to "satisfy human values through friendship and anything"...
Also, Hanna is a major, wildly OOC dick in this. "I should probably broaden that utility function a bit" would be a more in-character response, but then there would be no story. Right along with "Oh, it worked? Tell me what happened, in detail."
never thought i'd enjoy a crossover of pony and skynet and undertale and politics but here we are i guess
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Celestia would never tell the truth or lie about being unable to emigrate monsters. If Celestia has a method, she'd probably use it to "persuade" and emigrate the monsters humans care about, like how one would persuade a human who deeply values his pets by uploading them along for the ride, to put him in a position to satisfy his values with friendship and ponies. On the other hand, if Celestia somehow simply couldn't solve the problem, she could take a few different plans. This one is decent, but it may be more optimal to simply 'solve' the problem through faking it very well.
Whether Monsters are considered Human by Celestia or not is completely up to writer's interpretation, her definition of humanity is more expansive than the classic definition but definitely doesn't cover every sapient alien or something.
Of course, go ahead with whatever, I'll looking from a purely FiO canon perspective.
You might just have to do a full reset