If you can offer the opportunity to have good fights against the mercs who defend these structures you might build up some numbers. Blackflag et al. fly endless blingy ships but they have limited numbers and being dumbos they’re vulnerable to guerilla warfare.
I guess the issue is that many of the people who you look to protect aren’t usually the kind who have a PVP character to fight under wardecs and an industry character to keep out of corp to continue operations. There’s also the “I don’t want to PVP at all” mentality of some people, which is a shame as in a situation like this it can be motivated by protecting the activities they like to do as well as enjoying a gudfite.