I’ve always had my cats as outdoor/indoor animals, with no litterbox at all (Except when they’re very young). Never noticed any problems with smell, as cats are naturally clean animals and do a good job of simply finding a place to use the bathroom outside. I joke that indoor cats are like children (with all the maintenance that entails..), whereas outdoor cats are like delinquent friends that randomly show up to eat…
How do you deal with things like fleas? We have nearby squirrels and a small yard and are sure the fleas we dealt with were brought in by outdoor lounging from our cat.
I'd be more concerned about cars and coyotes. ISTR the half-life of an outdoor cat is about 2 years.