There does seem to be an element of consent from tribal leaders. When Killmonger shows up, he first makes his case before the tribal council, who decides that yes, his challenge is valid.Well really Wakanda needs to get past this whole hereditary monarchy/trial by combat stuff. They've got a ton of cool technology and apparently a high standard of living, but their political theory seemingly doesn't care about the consent of the governed.
We don't really know how the council members are appointed. They are called "elders", but I don't think it's as simple as "the oldest person in the tribe". W'Kabi certainly doesn't seem like an "elder". One might think that having a system where power is vested in representatives that may or may not be democratically elected, and that might represent different population sizes based on archaic traditions is bad, but some countries get to do that today and be called democratic.
(Yes, that's a dig at the USA in general and the Senate in particular.)
Matt Colville made a video where he took a look at Black Panther from a political perspective and how it demonstrated the nature of power. A notable thing is that while T'Challa is king, it is his disregard for W'Kabi's wishes regarding Wakanda's role in the world in general and the pursuit of Klaue in particular that leads to W'Kabi's support for Killmonger's claim, without which the claim wouldn't have gotten anywhere.I'm sure the MCU's target audience would go gaga over a Black Panther 2 that delves deep into political philosophy.
I haven't seen that one, but he was amazing on Leverage.Anyway, I know they've said they won't recast T'Challa, but T'Challa could decide to focus on being the ruler of Wakanda, enacting reforms and handling the politics, while a new person takes on the mantle of Black Panther. Right now, I'm rather smitten with Aldis Hodge. He had a great presence in One Night in Miami. Aldis Hodge - IMDb