The other Mishimas are ok and all, but none of them really have everything. I can't think of one mishima who has all of these:
demon's paw (ff2)
magic 4 (AK has magic 3)
hell sweep/alley kicks
bounding mid low punch, like a down 2
some kind of crazy high damage throw, like a giant swing
mid mid poke string that's useful in neutral and for pressure
something comparable to the 3+4 backturn flip for oki that AK has
shoulder smash that knocks down and splats for punishes
Heihachi has a lot of tools, but he doesn't have a hopkick IIRC and he has no demon's paw. I consider the latter almost mandatory for a character I use. The only thing I can think of that Armor King doesn't have is a backswing blow, but a lot of characters don't have one. Hunting Hawk can kind of work instead of slash kick, but not every Mishima has that either.
Jin has a lot of cool shit you can do with his back 1 stance cancels, but his EWGF isn't a launcher and he's very technical while also lacking the cheap shit AK can do.