Here is an idea for MK6....
There are unlockable stages in MK6 like in MKDA, hopefully they are more difficult to access and better hidden, but there are stages you can access that are classic MK Stages.. lets say the Pit or the Acid Bath from MKII(or Pit II, etc), the thing is on those stages you can side step and all of that so the controls would be comprimised... so you would just fight it out old school style on like six or seven new stages.... I guess you couldn't use them in arcade-tournament mode, but for two player, or you could turn the classic stage on and off on a secret option screen....