No. It should NOT be removable. You've been given plenty of reasons why. Also, I'd like you to point me out some documentary evidence it ever WAS removed in the field, as this isn't a simple job. Hacking it off may be, but you'd need an entirely new, specially-fitted piece glass made especially for the change in the canopy frame. And guess what, I doubt most airbases in the middle of the Pacific, many of which were just strips of crushed coral and had little more permanent structures than a few tents, had the facilities or equipment for fabricating the canopy glass. If a canopy needed replacing it came from a wrecked plane that was no longer flyable, a central supply depot IF they were lucky, or from back in the States.
The only F4U that should NOT have it is the F4U-4, as it was removed in all but the first few out of the factory and most -4s didn't have it to begin with. It's been requested a couple times to remove it from the F4U-4, but it should NOT be removed from the earlier marks.