The idea of splitting the center of power in Wakanda into two separate roles--Black Panther and head of state--is an excellent idea.

M'Baku would be King and Shuri would continue as Black Panther, serving as her own tech support. She wouldn't have to stress out about politics and M'Baku could deliver withering put downs to diplomatic idiots of all nations.

Just one thing: I'm not entirely sure this is a mutually agreed upon idea. It's possible that M'Baku may have been laying back for the whole movie to make this power play at the end.