The Admin's have definitely thought about this - but it would lead to everyone wanting everything to be un-stealable, which would be no fun. No one wants their items to be stolen, especially when they are meaningful. But that's one of the aspects of this game that we really do like and want to preserve. It's what adds an element of tension and realism - there's literally nothing that can't be stolen from you. Think of Confutatis' armor. It was magical infused into her skin, but that was stolen.
We've thought about it, and we want to keep everything stealable.