I’m having similar issues with my cat, and this sounds like a genius solution. No issues pooping in litterbox, but perfers books or bedding to pee on. According to the vet(s), he’s in perfect health, and he has multiple litterboxs in different locations, so I guess he’s just a weirdo. Dog pads in a litterbox seems like the perfect solution.
To my knowledge, theres no built-in functionality, but it should theoretically be very easy to make a bot for it. I might actually give it a shot when I get free time.