Hmm… tough choice. If I were in your shoes I would totally keep the cat doing what it’s doing – less litter, less smells, and the ammonia in the cat pee might even help to clean the drains. When I get cats I will be training them to use the toilet for both #1 and #2 – less mess, less smell, and I absolutely love the idea of a friend going to use the toilet and seeing it being already occupied by a cat. Sure some people might think it’s weird, but plenty of things in life are weird. If it saves you effort and you are happy with it, I’d say keep it as is!