I agree with those who say that a historical setting would make things too easy for the Predator.
I always assumed that the Predator's superior technology meant that they possessed above human intellect.
In order for the Predator to have an honourable hunt with humans armed with spears and swords he would have to lay aside this advanced tech. So the fun of seeing the Pred use his plasma caster is gone.
Also in order for a human without any modern/Pred weaponry to outwit and defeat them the Predator/s would have to make some pretty dumb mistakes. ( Not counting Jungle hunter, he died purely by chance when he stood in the wrong spot for the counterweight, he saw the original spike trap).
