FWIW, Outex has developed a rear port that provides visual access to the LCD and controls via a recent Kickstarter campaign; it should be available for purchase later this summer. They also offer numerous viewfinder options that mate through the cover to the viewfinder on your camera.
I wouldn't want to use it on a regular basis but for adventures in or around the water (packrafting, kayaking, snorkeling, swimming, etc.) or hikes and shooting in rainy/snowy weather, I think this is a viable option. It's certainly less heavy and awkward than a dedicated housing (been there, done that).
They offer a handful of different options to connect the camera + cover to a wrist strap, belt, chest harness, etc.
Of course, before someone could get along with a housing like this, they would need to have enough familiarity with their camera layout that they could find their controls without clear, obvious visual access to the shutter button, etc.
I could think I could live with the limitations of the design for the added range of conditions I could then shoot in.