That's a good point, and it would be cool. But at higher levels, in my experience at least, you almost never find lockboxes. So I'm not sure if there's enough demand for it to be implemented.
Something I would really like though, was if we could have a cross-server friend list. When we use random dungeon finder we're teamed up with people in our battlegroup, it would be nice if I could add some of them as friends to play with them again. I met a lot of nice people through random dungeons and I'd like to be able to play more with them. It'll probably be difficult to implement properly though, but it would be nice.