Very fine, as long as the computer uses X (the good less shitty one). xrandr can use a matrix to transform the entire output, so you can scale, rotate, move, or shear it as much as you're evil.
The biggest hurdle is getting shit past the GNOME developers. Wayland could implement a protocol that cures leukemia, and they'd still raise a stink about use-cases because it doesn't touch other types of cancer.
Technically that's compositor level stuff, and it probably can even treat it like an actual diagonal display and prevent windows from going there and everything.
This is a good example of why some of the protocols are taking so long. Once finalized, it'll probably somehow also be capable of handling... that.
With an accelerometer and a compositor written for that can probably even keep it level in real time. Tilt monitor and windows rotate to match automatically.
Windows command to rotate the screen, screenshot the desktop, set it as wallpaper, hide the icons & start bar... Functionally reversed mouse, and can't click anything.