I also see Mai as facing accusations of bias within the Fire Nation because of her love for Zuko. (I said love and not marriage because I imagine that a good part of what is giving her legitimacy as Firelady Regent is the fact that she is married to Zuko. In fact, I have this mental image of someone from the Earth Kingdom or the Water Tribes asking Zuko why he couldn't have chosen a regent whom he wasn't married to and Zuko having to explain this (including the fact that they're working on making Mai the Firelord's mother).)

It also occurred to me recently that Mai and Zuko might well end up having two weddings: a small, rushed, mostly private one soon after Ozai's defeat and a big, very public one sometime later that is at least half an international PR move and is subject to all of the planning that would go into a royal wedding.