Give Islam an equivalent to the Pope.
Not really all that possible, especially the Grand Imam equivalent.
To have a Pope equivalent, you would need a priesthood which Islam lacks. The priests, bishops, and Pope play a role within the theology of Catholicism (that of intercessor) while Imams do not.
The closest I assume you could get would be for Mohammed`s sons to survive and a more dominant form of Shiism developing rather than Sunnis achieving dominance. Thus keep the Caliphate within one family line that still gets rather sidelined... say by the Turkish invasions.
The Caliphal family loses all power after one or two goes at Empire, but they are very entrenched so nobody gets rid of them. They are then relegated to a Holy City where the dominant power can keep an eye/leash on them.
While a big power is in control, the family stays in Jerusalem. Then, when the area fractures, some enterprising family member moves the family back to Mecca/Medina where they then rule the Hedjaz more autonomously, but still being forced to pay homage to whoever currently is top dog.
The family is still the titular head of the Muslim role, and they play a massive role in Islamic jurisprudence, but that is about the extent of their influence. Still not very Pope-like but thats as close as I can think of. With a POD right at the founding, your going to be dealing with a rather different Islam to what we are familiar with.
Not really all that possible, especially the Grand Imam equivalent.
To have a Pope equivalent, you would need a priesthood which Islam lacks. The priests, bishops, and Pope play a role within the theology of Catholicism (that of intercessor) while Imams do not.
To get there, I think a succession of Mohammad's sons/bloodline is the most likely thing, which would change some of the early splits and subsequent writings. *snip*
A pope is a lot more than a titular figurehead - IIRC there has never been an equivalent doctrine in Islam to the Magisterium, giving Caliphs the authority to lay down infallible doctrine that all muslims are (theoretically at least) obliged to abide by. I suspect getting something like this will be a lot harder than merely arranging for a titular figurehead and will require a POD much closer to the founding of Islam.