Lets just say for a moment that one "could" take a standard low pinion dana 44 (for example) and flip it over...would you suddenly have a "high pinion 44" NOT NOT NOT.

With axle upside down, the gears would go the wrong way. So in first gear (no rear driveshaft) the rig would move backwards. No kidding. If you tried this and did not turn the inner knuckles around the ball joints would work there way out. Great plan.

Have axles been "flipped" and work correctly? Well, yeah.
Rear engine moon buggies have to, because the engine is facing rearward, therefor the in order to go forward the axles have to be upsidedown.

SD