I got a weird problem involving both of my cats (Siegfrieda, to the left; Kika, to the right).
Kika is rather particular about having her own litterbox(es), and refuses to use a litterbox shared by another cat. Frieda on the other hand is adept to the "if I fits, I sits, I shits" philosophy, and is totally OK sharing litterboxes.
That creates a problem: no matter if properly and regularly cleaned, the only one using litterboxes here is Frieda. We had, like, five of them at once; and Kika would still rather do her business on the patio.
How do I either teach Kika "it's fine to share a litterbox", or teach Siegfrieda "that's Kika's litterbox, leave it alone"?
Even when cleaned, she still refuses it. I think that she smells "the annoying kid used this box, now it's ruined forever!". The only solution is to clean the litterbox with alcohol, retire it from usage for a few days (so she forgets about it), and then reintroduce as if it was a "new" litterbox.
As such I don't think that the auto-cleaning box would help either.
I like the "private bathroom" ideas better, too, but, if you find yourself having to make a constant cleaning strategy work, after all, then on top of cleaning, perhaps try using something like Elimin-Odor after cleaning (if you didn't already try that) to specifically neutralize what she might smell? They claim it's designed to neutralize odors enough that a cat won't associate an "accident" spot with future bathroom eligibility.
I know there are feeders that use a collar tag to only allow food to specific cats. Maybe there's a litter box with a door that has the same tech?
I'll give it a check. If this exists (and if it's available in Brazil, and reasonably priced) it would solve my problems really well. Thanks for the idea!
I can confirm they make pet doors with this technology. If you can't specifically find a litterbox that has it, you could build a DIY box that does.