I agree. This genre is already somewhat 3D in you have a field to move around in. The main thing to upgrade would be the static backgrounds - give those some 2.5D styling and boom, we are off to the races again.

Oh, and add in some use of the map like we saw in Turf Masters on SNES and Splatterhouse 3 on Sega Genesis - let us enter buildings and such. Why do we have to constantly move left or right? Add some variety.