With the release of HeroStronghold v1.1.6, a new feature was implemented for limiting the number of regions of a type that player can build. For example:
peasant: priority: 1 limits: shack: 1 arrowturret: 2 citizen: priority: 2 limits: shack: 2 arrowturret: 5
This creates a permission node herostronghold.group.peasant that will limit that player so they can only build a maximum of 1 shack and 2 arrowturrets. Players still need herostronghold.create.shack to make shacks. If you don't set a limit for the group, it will not limit players in that group (so a peasant with herostronghold.create.landmine could still make as many landmines as they want). If a player has herostronghold.group.peasant and herostronghold.group.citizen it will only recognize the citizen limits because citizen has a higher priority than peasant.