Could we offer migrants a visa in return for a bit of crime fighting?

Aren't they all young men of fighting age?  Instead of Rwanda, send them to Ukraine as part of our commitment to Ukraine's security - and after x number of years at the front they can get UK citizenship, Foreign Legion style.  Lefties get to celebrate our commitment to European defence, right-wingers couldn't possibly complain about men who have fought for NATO being allowed to remain in the country.  Win win.  

I genuinely wonder how many small boat arrivals etc would be up for this.