Ok, first of all, you should make a section about it in the Civ4 - Project & Mod Development section. And start looking for people.
Converting the models is less of a problem than actualy extracting them from the game. If you can find anyone that can do it PM me.*found a way
I took a look at it and here is what I think:
For now, you should focus on the main races: Imperial Guard, Space Marines (Add the primarchs as leaders), Chaos Marines (scrap the chaos gods as leaders please. Put Warmaster Horus and Abidon the Despoiler.), Orks and that should be it as a start.
Also, you could use warhammer fantasy battles as a starting platform as they have already worked with things like hapynes modifiers and other things. You could probably use many models from there too (especialy for the orks and the like, they dident change much).
I also like the way they used chaos: Chaos is 1 religion, you get 5 diferent temples (one for each god and 1 for undivided), but can build only one per city. And each gives you diferent bonuses.
We could first make a mod that works like your attachment, but with compleate leader heads, data, techs, but no pyton changes. I could work out all the civiclopedia entries on my own.
PS. Can I join your team?