As a way to solve any real dilemma with what could occur with certain characters, would a merging be possible to overwrite characters should they step into our Prime universe?
The whole movie of "The One" probably explains it better for those who remember it. Basic summary was a fugitive went around killing alternate versions of himself since doing so would allow him to absorb that person and their power since the soul of people were split by the multitudes of multiverses. So by killing them one by one you increase your chances of being the only "One" who has that power within them.
So could the same be possible if we wanted to take certain people back to our universe? Durotan and Yrel for example. While it doesn't have to be done with death as the way to acquire these people, they could always merge characters should they step into the Prime Universe where we come from. If we took Durotan back with us and he were to step forth into Azeroth Prime then the spirit of the deceased Prime Durotan would be absorbed into AU Durotan. His memory would have the combination of whatever we're going to put AU Durotan through along with the Prime Durotan so he wouldn't be so confused.
The idea probably won't work with planets so Outland Prime still stands while AU Draenor stands as well.