Just create a new bastion like block that you must place down and that after a certain amount of time (1 week or something, idk how to balance stuff) takes all reinforced blocks in range and transfers them over to your group, maybe make it so that the block must be placed at build limit so you can't hide it from other people. Bonus point: if you are pearled and can gather up some friends to destroy those blocks for you before the time limit is done you can thus prevent someone from taking over your shit!

There, no super messed up convoluted and exploitable system requiring you to hold the pearls of all the bad guys or whatever at the same time required, strongest guy wins, the end.