If someone invades my FOB, I stand to lose far less than they stand to gain. I can only lose easily-farmed resources, easily-replaced guards, and the staff who weren't worth putting on direct contract. The invader can receive S++ rank volunteers, a prize far more valuable than the cost to either of us.
To give more people more S++ rank troops, I would gladly set all my platforms to zero security, but it looks like a recent change has made it so only really-high-security bases can give S++ rank volunteers. Thus, I need to weaken myself in a more sophisticated way.
How can I maximize my chances of losing FOB invasions, without getting the reward soldiers for invading me capped at S-rank? Are non-lethal defenses easier to breach than lethal? What weapon range sucks hardest? And can I use Key Security Zones to cluster my troops out of an invader's way?