This is what we are thinking of adding to the Womboat. My only worry to be frank would be noise from waves slapping up underneath.
This is the stern of Raven. To my mind preferable to platform but is a bit slappy at anchor.
Personally I'd be happy with an open stern even though yes a pooping might be , would be, more likely but the open stern beats the hell out of even the very best cockpit drains.