Question: With the ability to migrate questions, I have found quite a few duplicates on both SU and MSO due to questions being migrated from others sites.

Do we handle these as normal duplicates or should we just let them be?

Answer: 
This was implemented with the Mortarboard (bronze), Epic (silver), and Legendary (gold) badges!
I think this could be potentially refined into something like if you manage to get X amount of upvotes above the rep limit (say +10). 

I would call it Pro Bono, which is derived from the act of lawyers and other professionals taking on a case and not getting paid for it.