Any other implementation of Wakanda at Epcot, other than what you've suggested, would be laughable and a disgrace to the parks. So naturally I'm inclined to believe World SHowcase is exactly where it will end up being.
It is clear Disney is hesitant to add countries to WS. I think it is logistically difficult and politically risky. Wakanda would change that and give the creative team a lot of leeway in taking WS to a better future.
Definitely the type of creative freedom for Imagineering everyone here claims to want.