Resizing works for most games (with a few exceptions like Batman Arkham VR), but it's frustrating to do it every time the game is launched, even if as Jeremy said that it looks good to be active and keeping an eye on the stations, it's still a hassle.
What about if the Springboard launcher could open and close SteamVR's mirror view automatically when starting and stopping the idle video trailers?
That would solve everything since the latest SteamVR beta's mirror view has a new "center view" option without the black borders. Plus it shows the chaperone and system menu which would help a lot to be able to see when assisting customers.