We need as many versions as possible. The original Album remix, the original Movie/Album version, and Annihilation, plus the new ones for each movie. They're the best that ever was, after all.
Too bad Shao Kahn's voice didn't match the movie as well as the music. XD
...It doesn't help that most of the best MK music is the image songs, whether they're movie-related or game-related. Scorpion's "Lost Soul Bent On Revenge", Raiden's "Eternal Life", etc. The most ironic one is "Chinese Ninja Warrior", if only cause Sub-Zero is Lin Kuei. Scorpion's a Ninja. It's iconic as hell, but contradictory. Though to be fair, I think it was only Sub-Zero 2 that actually said this, and the first Sub-Zero may not care. That, and you know, they clearly didn't do research on what a Ninja is at the time and just made a very fun song that is historically inaccurate and even inaccurate in-universe. Which ultimately shouldn't matter because... it's just a song.
Most of these are done be The Immortals, so that shouldn't be an issue anyway. I think it doesn't help that the normal stage music just is... kind of eh? It's good for what it does, but rarely memorable compared to the stage itself. On the other hand, once in a while they can stick out, but it's hard to remember anything but the awesome image songs.
I'd also like them to come in as two characters at once, being semi-clone style, with Scorpion naturally being the "first" of the two if only cause he's the official mascot(and sometimes one of the core heroes. It varies). Spirits should be as many as possible. Everyone from the first game, as well as Shao Kahn, for starters. Both Sub-Zeros need to be a Spirit, though I could see only one version being playable, but a composite is fine too. With half and half each. Could even give the one from the Reboot timeline the Cyber Form if you want. Though if you do that, Smoke/Sektor/Cyrax could make for cool costume references. It's kind of awkward. Especially since Smoke is also a gameplay clone of Scorpion(but many are at some point, so costume references to them work too).
It's weird. XD