"Banishment" to where exactly?
I wonder if it could be codified into law. "If you've been responsible for x% of convictions, we will imprison you for increasingly longer periods", or "Top 1% of people when sorted by number of convictions will get a long-ass sentence the next time they get convicted."...
Habitual offender sentence enhancement or three strikes laws.
And in some countries, if you're a proven perpetual threat, the judge can issue a preventive detention sentence.
It has the advantage over the death penalty in that's reversible if a miscarriage of justice occurs.