[Suicide Junkie]

If the +MaxPop ability is working, you could do something really cool with planets:
50M/500M max pop on all domed/breathable planets.
City facilities provide +500M max.

Then use the production modifiers to make build rates be 1% per 10M people!

If possible, you could restrict cheap open air cities to breathable worlds, and force the nonbreathables to build domes for only +50M people... until they have enough industry to finish more advanced structures like arcologies or orbital habitats (++pop, but tiny footprint) in a reasonable time.