The latter part of your post is largely why we didn't go with this option, although it would be nice if they could take care of their waste themselves.

Not all at the same time, I grew up with cats, dogs, iguanas, fish, ferrets, hamsters and rabbits. By far for me cats have been the most worthwhile investment. Dealing with the small inconvenience of the litter box is something I shouldn't complain about since simply having my cats around for companionship has paid off such valuable dividends.