Heh, back in Alpha 5, I once made a stone wall that was 4 or 5 blocks thick and had a Y-shaped entrance through it (to block enemy sniper LOS). The only way in was a 1-block wide corridor that led straight to a very large room with 30 or 35 turrets fanned out (with stone blocks in between to absorb any blasts). I also parked a few colonists behind the turrets to repair them as needed. Got attacked by 6 raiders with explosives, no problem. Got attacked by 6 Centipedes, no problem. I barely had to do any repair work at all! Wonder how that would work in A6 with the bodypart system...
