I'm surprised that you say that at this time the Arabs didn't allow non-Arabs to accept Islam because that is contradictory to the teachings of Islam. I'm surprised because for example black slave Malik was one of the first muslims and he wasn't Arab but Ethioptian/Abbysynian. Moreover, the emissaries sent by the Prophet of Islam to the Byzantines and the Persians openly encouraged them to convert witth their whole states.

Another issue I think should be adressed, is the idea of including character of the Prophet Muhammad in this mod. This idea is breaching one of the fundamental rules of Islam. Depicting the Prophet as a game character could be a controversial move to say the least. Ofcourse it won't be controversial if this mod is only adressed to non-muslims, but I can hardly think that would be the case.

The period, or the whole idea of the Rise of Islam campaign is a matter of personal tastes ofcourse. I am myself a muslim but I don't find that kind of campaign especially interesting.