Thanks to @Frenzies. I had started a bumper cars level but gave up when the standard draggables weren't to my liking. Then I saw Frenzies' Motorcycle level and I knew it could be possible to have R controlled vehicles.
@B Hill Yeah, I made an R-designed vehicle before, but couldn't find a use for it. You could replace the back Draggables with Metal blocks to prevent players from just using it to Drag things around instead of using the actual mechanic. Maybe you could also find a way to put a win block somewhere. It's fun, though.
@B Hill Well, it would be cool if you could put a Win Block somewhere, as long as R vehicles aren't able to go there (maybe make it on Metal Pillars, as R's can't walk on them. I don't know what will happen when they're on a vehicle, though). Then the R vehicles would try to prevent you from going to the finish.