Kurt Angle, Jeff Hardy, Rob Van Dam, and Mr. Anderson?
Now, first to explain why those 4. The TNA group are the 4 biggest names that WWE has let go to TNA (who are still there) regardless if it was by choice or not and the WWE group have gotten the biggest pushes of any other wrestlers not named Cena, Orton, Edge, Undertaker, Triple H, etc.
All "locker room" or "behind the scenes" problems aside, we are simply talking pure talent and draw.
So, you could be potentially looking at a very different Wrestlemania...
John Cena vs Jeff Hardy (fan favorite vs fan favorite. If they ever wanted a great Cena heel turn, this would be a perfect time for it)
RVD vs Randy Orton (never got that payback for the kick in the head angle)
Kurt Angle vs Edge
Mr Kennedy vs Edge (payback for stealing the money in the bank briefcase)
RVD vs John Cena
Kurt Angle vs Randy Orton
Kurt Angle vs The Undertaker
RVD vs Edge Extreme Rules Match
RVD vs Edge TLC
Jeff Hardy vs The Undertaker
Kurt Angle vs Triple H