Very good point about the possibility of Mecca being the mother of harlots. But one must point out that this would bring a serious confussion.
The pieces of prophecy will not fall into place if Mecca was the mother of
harlots.
Look at it like this: This sect/order/church will produce the false prophet, not to be confused with the anti-christ.
Now before jesus's second coming the prophecy tells us that isreal will restore daily sacrifice. And the Holy Temple(Temple Mount) is currently controlled by the muslims. This is where they believe Muhammad the prophet left the earth. Now only the anti-christ will have the power to suggest muslims to give the temple back to the jews. Now lets look at it like this, if you were a muslim, would you let someone that you were fighting against (Jihad-the holy war) convince you to give the temple back.
I seriously doubt it. Because the temple is the most sacred mosque to the muslims, they fought for it for years. Now since the anti-christ can convince the muslims to give back the temple. I would strongly suggest that he would be a muslim himself to sign the treaty to give isreal the temple.
It only makes since.
I'll give you something to research
The Anti-christ is going to be Muslim most likely the Bashar al-Assad, King of Syria.
The False Prophet will be the next Pope most likely Jean Marie Lustiger, Archbishop of Paris.