The big living quarters aren't for everyone, especially with limited personnel cap (my idea was you don't need a 50-man living quarters for a radar base, 25 men are more than enough so why waste cash?); certainly not for defensive base setups. I'm personally using an "assault" base setup, which is much alike defensive in regard for 3 hangars on top, only with the difference of 4 (instead of 1) access points to storm the hangars by turn 3-4 in a three-pronged attack (sides proceed faster, the central group naturally slower, as it has to clear the lift), and no space wasted on defensive systems of any kind (and that's a LOT of space), so I have no problem running 300-personnel main base in the vanilla (150 sci, 100 engineers).
So with my setup, 2 big living quarters provide 250 personnel (forcing me to stop myself at 2 labs), that's 8 space, +hangars = 20 space, + labs&workshops = 24 space, +HWD&containment = 26 space, +2x psi lab = 28, +lift = 29, leaving me with 5 tiles for stores or whatever (2 tiles on the sides of the lift must stay empty).
The idea was to both make radar bases cheaper and force the player to spread research and workshops across 2-5 bases. But it would force less turtling and everyone should be entitled to turtling if they like so
Especially since it DOES make the game harder.