Interesting. So does he think he's worthy at the beginning? What's his internal conflict or does he have any?
The reason I ask, is that Captain America has a similar journey to discover his worthiness, but at the beginning he doesn't see himself as worthy, and when someone does, he's skeptical. He accepts a lesser position, even though it conflicts with what he wants to be, he's not convinced he's worthy of that, so he accepts, until his friend's life is on the line. There's lots of internal conflict there. He doesn't just rise to the occasion, he has to face something within himself to do so. He has to learn to stop going along with authorities and actually assert his leadership based on his instincts. It's not just that he's got external burdens, there's something wrong with him personally.
The reason Iron Man and Thor have to be torn down is that they start in positions of extreme power, so to 'grow' they have to shrink first. Steve Rogers doesn't need to be torn down, because he starts as a nobody. In order to not tear down T'Challa, you'd have to start him as a nobody, somehow unaware of his heritage, or else he'd be a static character that doesn't really grow. That's doable, but it should be noted that's different from the Thor, IM and even Captain America. It'd be more like Blade, I think.
When you talk about flashbacks to learning to be a king, somehow I think of Lion King, where the movie doesn't really work unless Simba becomes fundamentally separated from his kingdom.
I do like the set up for Killmonger though, that's clean.