This is an interesting idea...I've tried to do it myself, but fell short because of my lazyness : /
I lifted the camera to look down at a bird's eye view, had a (non-leaky) trigger to constantly make units fall downwards...The point of this was to represent gravity. The idea was a Super Smash Brothers engine. I raised the cliffs for ground and also used flat modeled boxes textures as the side of walls for the floor. I placed a small, flat region on those walls. If a unit was in that region, it would not fall. To give the flat effect to units, I simply rotated them. That's where I ran into my problem...
The unit's head is upward while facing left, but the unit is upside down while facing right. I was too lazy to make a seperate set of animations for facing right. You could try other techniques for units, but other than that, the idea of Tekken would take a bit of work.