Not a terrible idea (perhaps as an option). I've always thought that a sealed phone would be desirable. It would be much easier to water- and dust proof and maybe more reliable (fewer connections). Could get a much higher waterproof rating (definitely for swimming and maybe sport diving). Not sure how well bluetooth works underwater.
Charging, headphones and data sync could all be wireless. (And does anyone ever use data sync).
Maybe not for everyone, but it would seem like a way for a second-tier Android manufacturer to differentiate themselves.