You would be surprised what looks good on a tan wall. I would drag a projector out there to test with before going through the trouble of a screen. Assuming this is a "normal people" residence and not a 1%'er estate. Obviously if the client has a house staff then the removable screen is the way to go because the client doesn't ever have to touch it.

I haven't done a fixed screen outside but if i did...i would make sure that there was a simple mounting procedure so that anyone can take the screen out and snap it into place without a bunch of rusty bolts and misc hardware to deal with. Maybe some big @ss recessed magnets and felt covered metal plates on the back of the screen.

The motorized screen cons are bugs and bats getting smashed up inside. I haven't seen it with a filmscreen but with motorized bug screens i have seen a half dozen bats attached as the screen rolled down. I imagine if the screens were down and the bats were inside when the screens went up...squish!