Yes the core rules are very much in need. Universe of babylon 5 has pretty much none of the core rules, just changes and additions to core rules to fit in B5. For example there's no character generation rules in it, just few more careers and new event tables for old careers fitting in B5 setting plus campaign tables to give events specifics to campaigns(like Earth-Minbari war and so on).
In addition of variable use are going to be High Guard(ship creation rules) and any of the ship design books like traders&gunboats(and of course warships of Babylon 5) which can provide startup point for ships needed(though some conversion is required due to different settings like removal of jump engines and addition of artificial gravity. This doesn't apply for warships of Babylon 5 but then again how often your characters are going to use warships anyway?).
