The "dump" option is coming to mind that's available on the big trucks where airbags are they're only suspension method. But this would require some significant modification to accomplish the same feature on the Ranger....including converting from leafs to trailing arms.
A simple way, I suppose you could swap on an Explorer mono-leaf (the fiberglass Explorer single leaf spring) and install a Firestone or Air Lift load-bag kit and a compressor and air tank. Can't forget the dump valve for the bags. This could potentially lower the truck quite a bit for easy loading. Then when you're done with it being low, pump the bags back up to ride height/pressure. I'm sure the bags can handle 75% or so of the suspension load. This could probably also be done using a Ranger leaf pack that has been reduced in leaf count. The idea is to weaken the leaf pack so it will allow the bags to be useful in dropping the tail end.
IDK....seems pretty complex when there's plenty of stock trucks considerably taller than a 2wd torsion bar Ranger and they don't seem to have any problems with their height loading a couple of bikes. Hell I've loaded a 450 on paddles in the back on mine....and mines no where close to being stock height anymore.
'01 XLT disguised as a '03 Fx4 Level II
Big. Loud. Slow. Bright.