The only thing I thought might be hard would getting infantry to manuevuer under water, either with a viechle/kit or actually programming infantry with that ability. That water I've seen down there dosn't look that bad. And couldn't the underwater base simply be objects, that you can't go into? Maybe they could even be destructable. Perhaps infantry classes could spawn directly under water into suits (like how infantry spawn into the fighters in rise of kobol). Slap those an a few planets down there...But then of course you have the muchos viechles, and the different kits. Still I think it may be worthy of thought when you guys get farther into later releases, after all, you never know. An I would oh so much like to get me hands on one of those at at swimmers.... 

Futurama: You Can't Prove it Won't Happen