Could it be? Is Vin Diesel Kang the Conqueror? It could work.
Popular fan theory is that Vin Diesel will be playing the Vision.
I know; but that's pure speculation with no real basis in fact (except that Diesel talked about his vision in a tweet)
To be honest, I believe that Diesel would be a waste as Vision. Vision has traditionally not been a big action character. Vision hovers around; sticks his hand in someone's chest; etc. On the other hand, Kang can be a skilled fighter when he wants to be.
I think general audiences could relate to Kang traveling to the past to stop Ultron at his creation before he becomes an army that even Kang can't beat. The Avengers then come to blows with Kang because his solution is just to kill everything surrounding the known origin of Ultron (Avengers included).