Collaboritive Construction

I would like to engage the community to make suggestions for collaboritive construction. On several occasions I've teamed with other players to develop 1000+ prim sized projects. When we do we start off by establishing standard prim configurations; Share with Group, Copy, Modify. That at least allows us to work together for the time. Where things fall apart is backing up the project and working on the project asyncronously. We need some switch that when enabled will allow either a group or a list of avitars to treat thier visable prims as your own.