I used to run a flatbed on my '94 years ago. I'll add to this list...
5) You can pivot off of things with reckless abandon.
6) Can be used to bridge small gulleys for less capable vehicles.
7) Vastly superior for hauling and violently driving out from under 1,500 lb bales of hay.
8) Easy to build in a headache rack and mount a work light and winch up on top. Plus all that firewood won't jab through your back window any more.
9) Tool boxes can fit underneath beside the wheels, if you're clever.
10) Did you ever consider a hinge at the back end and a hydraulic cylinder at the front hooked into the PS pump with a solenoid a la the mile marker winches, capable of giving maybe a 20 degree tilt? Might take care of the need for #7...