Stupid idea because you would not be to find 16 fighters from 16 countries on anything remotely resembling the same level.
You ever heard of a Spanish MMA fighter? Or an Italian one? Or maybe a badass Czech MMA fighter.
If you were to chose fighters based on their abilities, one third would be Brits, one third Poles and one third Dutch kickboxers.
I live in my mom's basement and regularly dream of MMA fighters' toes.