There actually were Nubian pharaohs for a period (the 25th dynasty, to be exact). Not during the late bronze age collapse though, but while the Egyptian pharaohs from that time weren't black, they weren't light-skinned either. The actual pharaoh at that time was Ramesses III, who looked like this:It's got a black pharaoh what more diversity could you want?
The Total War depiction doesn't seem that far off, tbh.
Two things:
1. What did the paint on that look like before centuries of oxidation?
2. Egyptians were fat diabetics, but you rarely see that depicted in their art