This looks interesting. Perhaps as an alternative to the compounding upkeep, there can be yet another building or option that lets you reroute some production to support the colony's dense infrastructure? Like a universal -1 to all production for every 4 structures added. (EDIT: starting with building 13)
Also - for those that choose to fiddle with settings that still allow colonies to get up to 10 pop, the increase in population could also offset the personnel shortage and reduce the upkeep by 1 or 2 for every level increase. So at 7 pop, building 17 would be ^3 rather than the 6 pop ^5.
It might be beyond the scope of what you intended, and money isn't usually an issue later, but it just got me thinking and I thought I would share. Thanks for the mod! Definitely gonna try it out.