The technology is definitely out there but plastic screws and pins would be a lot less durable. Those who complain about loose ball joints now would probably die of a seizure if plastic pins ands screws were implemented
That said, I'd love water friendly transformers. I would like to have some sort of 'aqua fortress' that could float in a pool, house water friendly TFs and perhaps even have water squirting cannons/blasters as a gimmick.