As for the development of Arabic, do the Ebionites have their own gospel(s)? Perhaps an Arabic gospel becomes the important Arabic literature instead of the Koran in OTL.
UPDATE:I think they have their own Gospels, although the details were quite patchy at best.
Yup, the Ebionites have their own gospel/s, but I also sensed that Muhammad would probably write a so-called the Testament of Muhammand (or Gospel of Muhammad), which summarized the teachings and doctrines of Ebionitism, aside from translating the writings into Classical Arabic.