Xenonauts mod
This mod increases Living Quarters' capacity from 35 to 40. It can be introduced mid-campaign, but already constructed Living Quarters will remain with 35 capacity.
At the start of a game you have 10 engineers, 10 scientists and 10 soldiers. I usually get 5 additional engineers and scientists, and so the total space needed in the Living Quarters is 40, instead of 35. With this mod, you need only one Living Quarters.