Regarding points #1 and #2 and #3
#1) - You are going to put the coach through a space so narrow that the mirrors are what is holding you back? I doubt that, most paid drivers can't get it through a space as wide as the mirrors, never mind narrower, and why would you want to?
Not that I'd install cameras just for this, but I worked at a diesel driveline shop in Austin Tx and the door to my work area had about 3/4 inch clearance on the mirrors on some of the larger cab-over trucks. It was a tight squeeze, and going from the bright Texas summer sun to the inside of the much darker shop made it very
hard to see.
Cameras would have been nice a few times, but I think a ground guide or three is much more useful (and safe) way to maneuvering large vehicles in tight spaces.
That said - I'm planning on installing side and rearview low-light cameras when I finally get a bus. My night vision isn't what it used to be, and I'd rather be safe than blind.