It would be even nice enough for me if they only had like under ground bunker entrances so kerbals '' live underground '' and have like air strip of some sorts next to it where goods , parts or anything has to be delivered for missions or something .
Maybe add a few buildings next to airstrip / bunker entrance and it would even make a bit sense when some one sees it .
with this idea they don't have to build large city's and they can just say they live underground .
Then just 4 - 6 different settlements for example : one in the desert , south pole, northpole , next to KSC and i think there will be enough other nice places maybe at the Abandoned space center ?