YAY, I am not the only one thinking about this!

How about just a gigantic out door area, say 20 ft square, in a field with drops ramps streams, big puddles... a bit like Wetropolis on Full Metal Challenge. The 4 robots have to try and disable one another.

You would have to ban spinners, well I would, so that you can build in things like lifting arms and hydraulics for claws and the like.

Or you could have king of the hill, capture the point (I know a way to do it ) so many possibilities! Eeeeep!

I would go for something like Ripsaw MS1 but invertible with 2 pivoting spikes on the front, but thats just me!