I've done the protein powder, ect before. Some extra protein in the backpackers diet is a good idea. However,at this point in my life, mixing rice with protein powder does not seem too appealing. But who cares? Try it at home and see if it works for you. I do not see any health reason why you can't do it...

Sometimes I mix it into my peanut butter for trail, usually along with semi sweet chocolate chips.