What would happen if two opposing players send troops into the same tunnel from opposite ends? Do they fight each other in the middle, or do they pass each other by?
There could be multiple levels (vertical-wise) to the game to solve this. Units end up on an underground section of the map and walk in real time to their destination, allowing every tunnel entrance to lead to all other tunnels as well. It would also add another nice dimension to gameplay, though the underground section on most maps would most likely be small. This of course brings up the question, what if a scarab digs down to the lower level, will the passage underneath become blocked? Will units on different levels then exchange fire? I doubt it matters, because multiple levels (not just height) has never (to my knowledge) been done in an RTS before.
A Halo Wars Story: Once upon a time, there was a light bridge. On that light bridge, there were many covenant. When the UNSC turned the bridge off, the covenant fell. The End.