Ok hope I got the right category selected if not please sort it in the right one , How about the option to have you're settlement surrounded with bridges with 1,2,3 entrances. With turrets on top to avoid melee fighters, and stop enemies from getting in with traps on entrances alarms etc. alternating pure energy etc. I doubt sim settlements can change, where enemies get in. Power conduits hidden power generators protected multiple power generators or 1 or 2 vault tec ones etc.