Do you know how exiling worked? The place they go doesn't need to be uninhabited and the government doesn't choose where to send them the exiled chooses where they go, if they've been exiled the government just threatens them with punishments if they try to return and are caught. This is all opinion and you obviously disagree but if you think being sent away on your own with no guarantee of food or shelter for the rest of your life is less scary then spending time in a government ran facility with food and amenities provided for a set amount of time I question how well you've thought about it.
There is a way to appeal, the same way we appeal rulings today. It would still be a court process, you're talking like I'm saying tie them up in the middle of the night put them on a boat and push it out to sea. If found guilty of a crime worthy of exile it could be a punishment, then the exiled could appeal, if upheld they could stay. Simple as that.
As for breaking into groups see my previous concerns about your understanding of how exiling works. You talk as if you're under the impression we'd be sending them to a small deserted island. They could go to Mexico, England, Australia wherever they can get themselves too. There wouldn't be anybody taking materials they've been exiled, it would be on them to get whatever they need that's how exiling works, they can do this by foraging for it themselves or by joining a new society/country.
You're not talking about exiling you're talking about making a prison state like England did with Australia. That's not the same thing at all.