I feel like Marvel should go a similar route as with casting Thor for Black Panther. Get a lesser known guy and then surround them with a great cast and director.
For me, there's no better pick out there for Black Panther than Tongayi Chirisa
His biggest US role to date was as Friday in NBC's Crusoe. Here is a clip reel from that role:
He fits Black Panther in the same way Hemsworth did for Thor. He has the right look, is the right age for a franchise, is African, and most importantly, is a good actor.