[Fyron]

The best suggestion I have is to start small... Don't try to implement anything from Babylon 5 Wars (pretty much ever; its an unwieldy, complicated mess), don't try to just port the SE4 mod. Start with the core races, and only give them 2 or 3 thematic weapons each (it's AOK for there to be a set of weapons everyone can use). Try to have as many shared items as possible, especially in the more basic stuff like ship sizes, armor, and engines. Don't try to make a per-race set of unique thematic facilities from the beginning; get a core set of facilities working first. Once you get the core working, you can think about adding more auxiliary races, weapons, and specialized racial armors/etc. Basically, plan out a roadmap, where the first few milestones feature primarily universal, shared items. Save the nitty-gritty details for later, and you'll be able to get much farther, faster.

And most importantly... post the milestone builds for early feedback! Don't think you must get the mod "complete" before sharing it. Release early, release often.