The rebels are in for a nasty surprise if they think nuking the jump gate will trap the EA fleet or prevent reinforcements from arriving. The Nova has its own jump drive. :twisted: (Even if it doesn't in your game, there has to be something with a jump drive which can get to another star system under its own power in order to build a jump gate there; in the conventional B5 universe, that's the Explorer. So the rebels are still going to get unwelcome visitors when one of those shows up flanked by a few Novas...)
The Babylon Project was intended to provide a neutral place for various races to negotiate their difference and thus prevent war. There won't be a Babylon 5, or for that matter Babylon 1, if there are no aliens! There are, however, other space stations in the B5 universe. There's a ring-style space station which appears in the film "In The Beginning" and which is referred to, in the wargame "A Call To Arms" at least, as an Orion starbase. There's a picture
here.