I have been rolling this one around in my head lately. The use case is for groups where one member is maintaining one or more high level safe houses and needs the group to help, especially if they are away for a vacation or similar. What I was thinking was adding a new "outpost" build item that anyone in the group of the person who places it can visit. The visitors would not be able to interact with anything at the location simply by visiting the outpost, but could view the area and drop a flare there. The outpost should have a reasonably long life, similar to safe houses. Perhaps they could be upgraded through some method as well to increase lifetime, like safe houses.