I'm seeing a market for pee-valve extenders. A threaded, hollow bolt attached to a long tube. Screw that into your valve when topside, run the hose over the side of the boat, pee with impunity.
I will tell you this, besides the end-of-the-day removal, the fear of a UTI, or that moment of "uh oh, did the cath pop off" these things are absolutely genius. I can't believe I waited almost 100 dives in a dry suit before getting one.
I'll pee in the gravel parking lot (maybe a bit too close to the car-sorry Rjack, at least it was raining) but I wouldn't just let fly on the deck of a boat.