Haha ok.....I think IF you can get her to sign off on it just get a porta pot and store it on the boat somewhere. Being a guy I don't see the big deal with pissing in the water but she's a woman
You both want two different boats, you do a lot of watersports so a wakboard boat would be best for you. If you get a boat that is bigger and has a potty on it then you will sacrifice your watersporting activites no doubt about it.