You'll need am early change in stance on the status of language in revelation and ritual, basically. The problem is not that Muslims 'all must speak Arabic', it is that because of the special status of Arabic as the language of the Qur'an and of religious and legal scholarship, it became the entrance ticket to a global community of highly respected leaders. A bit like Latin in Western Europe, except that there was still a significant community of people who spoke living Arabic, too. It probably won'rt be possible to remove that status entirely (the original revelation was in it, and the holy cities are in Arabic-speaking lands), but if the early position on translation were different, ironically if the early Muslims had been as bent on converting the infidels as many modern people think they were, we could see the early emergence of a Greek, an Aramaic, a Coptic and Persian-speaking Islamic culture much more distinct and separated from the Arrabic core than they were IOTL.
I'm not sure that would be a Good Thing, but iot could certainly result in some very interesting developments down the road. Would make religious separatism and 'heresy' easier, for one thing.