I have no horse in this race, as I'm sticking with RM2. But reading this, at a time when I'm reading some great fantasy set in the medieval Middle East, it struck me. Many of the Arabian Nights stories involve magicians summoning djinn, ifrit, marids, and other celestial/infernal spirits. These would be magicians summoning demons, essentially.
I always go the route Hurin went - I would just homebrew it and say that culturally, there are magicians who have focused on demons rather than elementals. Or you can really go general and say elementals, djinn, demons, all of them are just extra-planar beings, and make them interchangeable.
The rules should never obstruct the fun or creativity of the players or GM. They should create a context to guide balance.