Unlike flat panel displays, projection screens can be mounted in any number of ways which allows them to be removed easily. Since they hang, like a picture, and only weigh 15 or 20 pounds, they are easy enough to put up and remove.
For a window, by example, you could hang the screen several inches in front of the window. You could still put light blocking shades/curtains up on the window, and it would only be partially covered by the screen, but when you wanted to use it, you could cover the window, and when not in use, you could open the curtains and get some light into the room.
Same with pipes, which could have the screen floated in front, then take the screen down should any service work need to be done in just a matter of seconds.
This space you have really is ideal for a projection setup in many ways.
If you want to keep the size down some, then the LG PF1500 may be worth consideration. It is LED driven and can handle a 110" or so screen without much issue. It turns on/off nearly instantly and should last you for about 10 years with normal use.