Edit: Also, one more thing:
Make an Imam certification, or even better, an education in all Western countries. Make it required to have a valid certificate or a credited education to be allowed to lead Muslim congregations. This would limit one of the sources of radicalization.
The same goes for teachers and administrators in religious private schools, which have also been a huge source of radicalization.
This might present some problems.
I am speaking from the perspective of the United States.
I am not familiar with how all western countries enshrine "freedom of religion" into their governing system.
Is it embedded in their state(national) constitution?
Is it embedded in national laws?
Is it as a result of judicial decisions?
In the United States, the "freedom of religion" is embedded within the First Amendment of our Constition and subject to interpretation by our judicial branch.
[
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the government for a redress of grievances.]
Government in the United States has generally tried to avoid legislating religions on how to practice their religion and (to my knowledge) has not been involved in legislating how a religion chooses its leaders or ministers/priests/pastors/imans, etc.
I think that you would run into the same problem were you to attempt implementing this on teachers and administrators in religious private schools. While state governments (I think) generally do set minimum standards for all teachers (public schools, private schools and parochial schools) in a state to obtain a teacher's certification they do not extend to religious classes.
So I believe that this would be a "no go" in the United States were you to attempt to do this via government law.
Now were the religions in the US to do this voluntarily, you could probably avoid the constitutional issues.
However there would be downsides to this approach.
---doing something like this would be voluntary (could not be mandated by the government)
---religious "governance" in the US is fragmented and varies widely. Roman Catholicism in the US has a number of cardinals and bishops who report to the Pope in Rome. Some other major religious (ex: Lutherans, Baptists) denominations have national boards that may help set/coordinate church policy. [But even those can be fragmented as I think you have 2 larger Lutheran denominations and then some smaller ones]). Then you have denominations of lower membership or even individual church congregations that are independent and report to no sort of central religious authority.
---how (or even if) they were to implement this would be inconsistent
And were you to attempt to require any sort of iman or teacher certification on just Muslims in the US...well, let's not even go there.
And again, this may be more feasible in some other western countries, but I don't think it would be possible in the US.