The Internet really is littered with these. I think there's one for Civ 3 that went really far and some started attempts for Civ 4 that never went off the ground. I've been dying to get into modding and something big would be nice to put on my CV, now with Civilization Network, whatever that is, the timing feels right

First thing, in WH40K the Imperium of Man stretches over millions of planets and technological advances are outlawed. It really doesn't scream Civilization, however everyone that uses the WH40K-franchise does the same thing: Keep the back-story, violate everything else and explain everything with a Warp Storm. I think it would be good to do the same thing.

All I really want is to use all the pretty units and squeeze in the fluff in the technology-tree and pop-ups. Back-story would be that the years are 20 000 - 30 000, the time when technology is still advancing pre-Horus Herasy, and a Virgin World that have been trapped in a Warp Storm is revealed. Everyone is there to war and colonize. Then of course, the Warp Storm closes again.

The Space Marine-technology tree is basically going through the different types of power armour (will look cool with veterans late-game), there are no Tyranids, Tau and Necron. I was thinking that Eldar and Orks are, at-least in the latter case, really aggressive barbarians or the new "City States". Then the civilizations would just be Imperial, so the technology tree would spread over either advancing Imperial Guard units, Space Marine units or Psyker/Chaos (for both). Leader-heads would be governors or Commissars I think, no famous Primarchs or the likes.

I'm hoping that it would be relatively easy to make, since it would essentially just be new units, but still stay very true to the fluff, even though we would have to call it WH20-30K or something

This topic is for theorize and dream away. The Emperor orders you to go nuts