One of the first things I would do is expand the roster, each wrestler gets their own slot while each attire is from a different year. For example with Triple H, he would have his regular attire from 2000, but if I went to 1998 he'd have a DX attire, if I went to 1996 he could be in his Blue Blood attire, if I went to 1993 be could be his Terra Ryzing gimmick from WCW, if I went forward to 2016 I would have his attire from WM32 along with the shaved head.
This also changes with the moveset. John Cena wouldn't have the STF until 2006+, Kurt Angle won't have his Ankle Lock til his 2001 attire, so forth.
I know this is sort of possible right now using GameShark hacks, but I don't think you can make extra slots. I only know its possible to do Attires 5, 6, 7... but we're still limited to the 64 wrestler slots + 18 CAW slots from what I know.
But to be honest I havent been on here in some time, have we ever been able to get more than the 64 + 18 wrestler slots?