I was actually planning to do something like that to begin with.

No real numbers are quite made outside the social engineering bonuses/penalties, so I'm not sure exactly what would be balanced but I do intend to try and implement a limited number of AC [and AX] Base Improvements. I first intended to represent them around a base with letters, but terraforming proved to be more...space-filling than I intended in the Map Prototype...
What I've come up with for the map:
As you'll notice, each base seems to have its own "section" of influence that is further cut into four pieces. This is the Base Zone and Sector idea I've come up with. After a Base of any size is founded, it gets its own "zone" -- the NES equivilent of the Base/City radius. Rather than bothering with worker numbers, all areas are worked for all they can be by the population of a base.
But that's where Sectors come in. Bases are divided into four sizes: Outpost, Medium, Large, and Metropolis. An Outpost base has a maximum population of 4,000 and a minimum of 1,000 [unless the base was recently attacked], and can only "work" one sector of the zone, as an example. Only a Metropolis base can work the entire zone at once.
Zone sectors also work into terraforming -- rather than having the choose where exactly to terraform something within a base radius, one simply has to choose the sector to Terraform. Outside of base zones, terraforming works based on exact location, distance from safety and/or escorts, and proximity to Xenofungus.