Substitute for refined white flour to make fried potato wedges crispy?
You could substitute any flour you like, the purpose of the coating is to give it some extra crisp when frying. I would suggest maybe rice flour or you could use whole wheat flour but the taste may be different. 

IMO, I would skip that step altogether though. A potato wedge is just a french fry cut in a different shape and we don't dredge french fries.