i’m confused where are you trying to go with this line of thinking? If you fly them in a C-17, you need clearance for the C-17 and use of an airport. A V-280 will be able to fly directly to where it is needed and will be able to perform its mission almost immediately.
The aircraft is also all weather capable, and can fly at altitudes much higher than any helicopters. Even the Defiant.
I thought it’s max altitude was around 6000 ft by the blurb so unlike a C17 they are never going to fly above the weather and I wouldn’t fancy chugging across the Atlantic in the winter at 320 MPH below 6000ft in case of a rapid deployment requirement. I mentioned clearance as I might imagine some countries having issues with military aircraft so visibly transiting through their airspace where as a C17 to those on the ground could just be another airliner.
That’s all
BTW you are still going to need fuel, etc to fly its mission.