4 direction dump? I don't think automatic dumping dirt on the cab is a good idea, union back hoe operators will grievance the truck builder to say that the equipment is taking their job of dumping dirt on the cab. . .

One of the problems with a side dump is operators can stand a rear dump on it's tail gate if the load sticks. A side dump would lay in it's side with less effort.

I've seen track dump "trucks" with a 2 way dump and swiveling cab to eliminate turning around.