Well in there lies the problem.. those four dinky @$$ bolts are charged with transferring all the power to the back wheels.
The joints in the 3/4 ton trucks are torque tube, as well, but far heavier duty.. it would be cool if somebody made that sort of joint with the right size splines on either end.
The only real advantage I see to torque tube rigs, is if you happen to drive thru some old barbwire or fence wire in tall grass, it won't get caught up in the spinning driveshaft.. other than that, the "open" design used on the larger trucks seem to hold up just fine exposed to all sorts of muck and crud.
