As an originalist, I think that as it stands, the Constitution does allow the worship of a 'One God', including Allah. But that can and should be amended. I think that most muslims may be able to get by with ankle bracelets, perhaps. And I don't want them to have the 'out' of pretending to leave that religion after an amendment is passed. There must be a new status of citizenship: the muslim citizen, who has less privacy than the rest of us.
We probably would not need an amendment Arthur if we just get past accepting every oddball belief as a religion just because someone has figured out they get all sorts of protection by such claims. A simple test (feel free to expand upon this) can be made for a valid belief system.
1) If your belief system instructs you to kill nonbeliever's it is not a religion.
2) If your believe system instructs you to kill those who disavow or leave your belief system, it is not a religion.