I would love HTC get the rivers sorted for the next version of the terrain editor. I have hope as they are going to have to redo them anyway to match the rest of the new terrain.
I put some rivers into an earlier version of the MA terrain I'm working on, but had to delete them because of all the bugs. It had several spawn points where you had to cross the river over a bridge to reach the nearby base.
The only issue I can see about having two bases so close together would be someone spawning on one side and getting immediately pinged by the enemy AA across the river. The VH would need to be sheilded from the opposite bank by a small hill or something.
Assuming HTC do get the rivers working in the next version of the TE, it would be possible to implement this idea to a degree with existing objects, as the bridges are already in there. You could make a couple of V bases that would be captured by destroying a town rather than just killing the AA on the base. The towns would go either side of the river and the V bases a bit further back, so the AA could not reach the other base.
BTW, here's what rivers look like in the current version of AH:
