To the OP, you don’t automatically need airbags.
And in your case doesn’t sound like you need them at all. Or possibly any additional suspension help save for a stiffer sway bar if the body roll is not acceptable to you.
If you don’t like how it rides, slap the timbrens on it and shim then to your preference.
Not sure why you don’t think the bottom leaf wedges won’t help. They will absolutely stiffen the suspension, unless you mean in conjunction with the Timbrens which may hold the truck up high enough to not get into the bottom overloads capacity. Or by wedging the springs, not make use of the Timbrens.