I think it would be cool to have 2 dueling/racing B&M's. They would be floorless coasters, and there are a couple of ideas I thought of.
1. I would build it so the stations are on top of each other. The lift would be a lauched lift, and the odd thing about this is that right after the top train leaves the station, it does half in inline twist, so the people in the top trains could look down on the other train, and the bottom train could look up. This may not work, since some people would think it would be cool to spit on the train below.
2. The rest on the ride would be exactly the same as a normal dueling/racing B&M.
3. The other idea I had was that the train that started on top, would pull into the station on the bottom, and vice versa.
If the way I want to set up the stations isn't feasible, which I think it is, it would still be cool to have the stations like a normal dueling/racing coaster, and just pull into the oppoite station. Either way, these coasters would have great capacity.