Homeworld has some great mods, including an interesting Star Wars vs. Star Trek one, and I'm pretty sure someone already did Babylon 5 ships. The Star Wars ships in that mod are far better than anything Lucas Arts has released, albeit they haven't made a pc space flight sim in a while. The game just has a great engine for that type of thing. If only we could marry a pared down homeworld engine with Gciv.
btw, B5 is also my favorite TV space genre. But instead of waiting for the "mod community" to release something, let me encourage you guys to give it a go. There's no better way to learn things like this than to pursue a little pet mod project. Othen then event writing, which, let's be honest, is not very labor-intensive (though perhaps testing intesive), there doesn't seem to be much modding activity around here. These types of communities are usually made up by who really love a genre or idea enough to throw some time at it, um, kinda like you guys