Penal legions... there's an idea.

I think that suicidal missions are not required. There are enough bad ones already. E.G. mine clearance.

And they've got a choice: listen to the teacher, or in 1 month's time they are going to Cambodia/Afghanistan/wherever trained or not. They have a quota of mines to safely diffuse and then their tour is done. The number of mines depends on the crime of course.

Other tasks like lugging aid to dangerous areas could be given. Say a 5 man team with one soldier overseeing.

The best can afterwards join the army proper, or possibly be pointed to wards a mercenary outfit. They are violent people. No point in pretending otherwise, so use the skills.