Nine Princesses of Equestria

One could easily do a spoof of Zelazny's Amber series in an MLP setting.
Just imagine an alicorn princess regaining her memories and returning to Canterlot to find out that Celestia is gone and that there is a power struggle for the throne of Equestria with Elements of Harmony (instead of The Pattern) and other alicorn princesses and noble unicorns viyng for power.
That could be rather nifty, even if it would require some very significant character motivations to set them against each other instead of just solving everything amicably like they ostensibly should.

The analogies pretty much write themselves.
*Celestia is Oberon - an ultimate monarch that suddenly vanishes.

*Sunset Shimmer is Corwyn - a princess stuck in an alternate dimension. Also, I just like Sunset Shimmer. She is the best pone!
*Twilight Sparkle is Random - she gets Sunset out of EQG verse and kick-starts the whole shebang. She also ends up the new capital-P princess and ruler of the Equestria.
*Rainbow Dash can be Julian. Someone with no real pretenses to the throne, but who enjoys physical stuff and guards the realm and is well trusted by all. One should think of a motivation to cause her to fight... well, to try to stop Twilight/Susnet combo when they're going to Canterlot, but that can be arranged through some clever writing.
*Fluttershy can be Deirdre. I mean I really don't ship ShimmerShy but Deirdre was entirely 100% pointless in Amber Chronicles, so it really doesn't matter who you put there, really. It's just there to get the count to nine.
*Rarity can be Florimel. Everybody thinks she is the dumb blonde, but she is reasonable in magics and has the social charm to always be on the winning side.
*Cadence can be Eric. Ok, granted, that one is a bit of a stretch, and you need some creativity to not get massively OOC, but she is a ruler of a country, in possession of a powerful magical artifact (Crystal Heart), and has an outstanding grudge with Sunset (that last one is taken from The Freeport Venture, which is my personal head-canon and way better than the comic).
*Shining Armor gets to be Gerard. Strong guy, good moral compass, not the smartest tool in the box.
*Luna can be either Llewella as a ruler of realm of her own who has no interest of taking over, or Benedict as the most powerful and capable of princesses with clear authority and power to just take over, but no desire to do so. Either way, she has to be sort-of excluded from the struggle, because she is clearly a superior princess and a clear successor.
*Blueblood can be Brand. He makes a deal with Discord to get alicorn-level powers that put him on par with other candidates, and also drive him stark-raving insane, nearly destroys the Tree of Harmony and generally does everything Brand did in Zhelyazny's book.

*Starswirl The Bearded can be Dworkin - somebody who has not appeared in Equestria, is likely to be more-than-slightly insane, and knows a lot of things nopony was meant to know.

Elements of Harmony are clearly The Pattern, whereas the Tree of Harmony is the True Pattern that lies underneath even Canterlot, and that has been damaged by Discord.

Discord is Logrus/Snake.