I guess I can make an addon mod for CU since too many people asked for this option.

"The Belt" is a fun mod in this regard. Maybe you can cooperate.

I've been playing with both The Belt & Colonize Unlimited active, and I think they almost work together already, as they change somewhat different aspects in the game - this mod does not touch asteroids and the other does not affect planets.

However, the building in The Belt mod, used to give asteroids habitability, does not give any if these mods are combined, presumably because being incompatible with this mod's system(?).

Perhaps by adding some other type of building from this mod to those asteroids could help, but haven't yet researched them all and couldn't find a list of them. So currently, if these mods are used together, asteroids can be colonized, but only with robots as their habitability is stuck to zero.

I still like to use them together...