As some have suggested, I think the game would be improved by increasing the colony improvements available. A few ideas on how that might be done...
Instead of terraforming tech, which seems odd for earthlike planets, I would like to see the core worlds increase on a timed schedule, that becomes slower as the distance from your homeworld increases. By early end game, the home world max out to a class 20 world. Somehow the game should recognize the power of core planets vs frontier planets regardless of the planet class
I would like to see all system uninhabitable planets given a value of one to allow the building of a factory or research lab with a constructor instead of a colony ship. The factories could be linked to the system ship builder to increase production speed. The ability to build these improvements would be tied to a tech an should be expensive.
I would like to see the econ, research, influence, etc starbases built on the influence resource as it was in GCII, instead of beside it. I am not referring to the mining resources like antimatter, etc. I assume that, as it is, others can also build nearby starbases to claim it;s influence.