While I don’t have any casting suggestions, from what I’ve read it seems that the attribution of this portrait as being Shakespeare is all based on circumstantial evidence - that it’s from the right period, that it once belonged to Henry Wriothesley and that it looks a bit like the Droeshout print (which I don’t see myself, but I’m not an art expert) . Yes, it’s quite possible it is Shakespeare, but then it’s also possible it could be someone else entirely.
I always thought that the traditional image of Shakespeare (goatee, bald forehead with long hair in the back) kind of looked like a Klingon, except without the bumps on his head.