Convert has bee tried. Why you think expulsion was the preferred method?

Interestingly, banishing people has been done for centuries. It could be applied to those stealing, etc. These people could be banished for a year, or 100 years.

It was an easy solution, and worked well. Better than prisons.

But since it is declared a human right to settle in a different area of the globe, it has tension with the concept of nation state.

We often hear that nation state is a new phenomenon, and in terms of law, that may be the case. In effect, it has always existed, from the village/town/city level to regions and whole continents. This too has been the idea behind "indentured servitude", where prison sentences could be swapped for "working off a debt to society, in some colony. Of course it was abused for commercial profit.

Compared to galley service (Spain/France for instance) or outright slavery in Turkish and Barbary coast areas, it seemed reasonably mild.

But to clean house, and make the country secure, I guess a exit of not only sharia lovers is needed. Their enablers too.