I'm sure it has been done.............legally is the question :B
Pumping water from a river to use as showering and flushing toilet is no different then swimming in said river.
Using one waste containment holding tank is nothing new either. Wasn't that many years ago RVs just had one waste tank for grey and black waste water.
Pump with suction screen and filter on discharge supplying your 'get away' camper........just need power source
Then means of collecting/containing all waste water to be hauled away and properly dumped