Space Empires IV is more along the lines of a Space 4X Wargame than anything else. I got tired of waiting for Masters of Orion III and decided to pick up this little independent publisher's gem. The publisher's
website can give you more details, but I'll say that SEIV
is insanely complex and customizable. SEIV is frustrating at times (especially at the start), but you can tell the game has incredible depth. I'm on my fifth "starter" game because I keep finding better ways to expand/optimize the beginning game. My latest snafu, I think I created a GVD Typhon that didn't have enough storage space for more than 1.5 waves of fighters (30 fighters), so I had to tweak the design to allow more cargo and a few less fighter bays. Of course, by the time I realized this I already had 5 Typhons in development.

One idea that floated around here sometime long, long ago was tactical and strategic MODs for other games to expand the FreeSpace Universe. For example, there's a Homeworld MOD based on FreeSpace. Space Empires IV (Gold) would be strategic on a grand scale.
I've found a Vasudan "Empire" set which isn't complete. It's better than I expected, but needs a little work to polish off the rough edges (and to fix several inaccuracies). I'll post the results here if I find two things (a) a FAQ that will show me how to finish it and (b) the time to actually do the MOD work.