When I move, I intend to have cats in my life again; but I can no longer manage a regular litter tray, so I've been investigating other options. There's an excellent raised one, but you can't get it over here.
So... shout-out to my online friend Ruth, who said "get one of those rabbit hutches on legs". You can put a litter tray in and leave a door open for the cat, and you can open the top to muck it out. Utterly brilliant idea!