I agree that SEIV and GalCiv both are excellent games, and I'm glad to have them both. Each of the two games has a different focus, and IMO they complement each other very nicely.
Regarding the modability, I have to agree that this is one of the very strong points of Space Empires IV. And from what I read about Space Empires V, this gam may well take modability to a whole new level that has never been seen before. Yes, that's a superlative, and I'm usually very careful with those. But show me another game where you can actually mod each *formula* of the game engine, put in or take out factors, or even totally rewrite it. Or where you can not only add new weapons, but also add new weapon *types*, new damage types etc. Of course, you'd have to mod the AI too if you want it to use new features, it will not be able to adapt automatically. But Space Empires puts its focus on multiplayer anyways, its AI was never one of its selling points. That's where GalCiv has one of its strengths, and that's what I meant when I said that both games complement each other. It's great to have them both.