I dont know If this has ever been covered but many people say its a great idea. As a Builder and maker of jewelry, I find it difficult to fit jewelry that would fit the general population. So I would find it extremely useful if you could add a check box in your friends list to give the ability to edit items ON an avitar, I've heard so many people complain, I don't know how to build or edit things on me. So when they get new jewelry,hair or clothes they don't know how to make it fit right. It would be useful also for me as a jewelry maker to fit my jewelry to those who cant do it themselves. It just needs to be a check box like we have to edit other peoples items. I know it would probably be a major undertaking but useful none the less.
Many of my friends who are jewelers, hair designers, and skirt/clothes makers have the same issue. I even made an alt to fit things better but everyone is so different in size and shape it makes it so difficult to make them fit right on people who don't have a clue how to shrink or move a piece on themselves.
Ive met people who love to shop but hate fitting prims to themselves. I'm a pro builder in sl, for me its a simple task, for others its like fitting jigsaw pieces to a puzzle that has 100000 pieces and frustrating to them.
I think this is something Linden Labs should consider for a future update.