The unguarded ones ... Gunrunners is meant to be the tough to earn access alternative to thoseCraft slowly in safety in Gunrunners vs craft freely in dangerous places.
Really if you think about it the BoS would logically have an Advanced Workbench. Joining the BoS should be harder but with the Advanced Workbench as a benefit because atm they have no huge benefits of joining. The Enclace should also have an Advanced Workbench following this logic after all they have PA.