I think one of the big issues with SWR is that they greatly expanded aerial movement, but they didn't really add much in the way of attacks that use all that additional space on the battlefield, so combat is too flighty.
Rather than simply restricting it to IaMP movement again, I think it'd be interesting to reinvent the system so that aerial combat was more robust; for instance, being able to hover and do floating combos in midair, and having better vertical normals (pretty much every 8A leaves a lot to be desired...) so that the players could fly around in the air and open up a whole new dimension for zoning. It'd be highly experimental though, and would take a lot of patching to get right, probably. Still, I'd rather see something new than just go back to IaMP.
My favorite thing about SWR is all the alternate specials, which lets you customize each character to suit your preferences, so I hope that stays in the game.
Do bring back the second melee button though, please T_T