Hey Scud
There are many Airline Jocks who were bush pilots with thousands of hours of scud running / short field / charter/ relief opps / medevac/ floats/ bla bla bla. Sure they might not be current but have certainly demonstrated and do possess the ability.
They have nothing to prove . However I cant say there are too many that are currently bush pilots who have been 744 Captains yet ( and they still have to prove themselves in that arena) . Welcome to the career ladder !
If you are merely saying , that current Airline guys might find G/A a little challenging as its different to what they are " currently" doing. Sure I agree it might take a little while to get back into it. But its more than possible. Just as its possible for bush pilots etc to become 744 Captains etc.