I don't know if I'd go that far. It's almost certain to make him look a whole lot sillier, and that's exactly what casting Momoa is supposed to avoid
How can you even ask that question when he played beside Emily Clarke for an entire season of Game of Thrones? She is completely transformed in my mind by her blonde wig.
What's more, he looks different in almost every role. Are you telling me that the average person could watch Stargate and say it was the same actor as in Game of Thrones or Conan?
Google his name and look for images of him without dredlocks. Then imagine blonde hair and I am sure you would be hard pressed to think he would look wrong for the part.