oh and if you just want to have 2 choises and no need to switch go with 1 as normal upgrade and the second as the crate-spawn-thingy
edit to answer your edit:
the crate that needs spawning is the same kind of crate a dead unit would drop if shot by a Salveger (GLA) or even a crate that can be found on the map (cash and rank bonusses) it does not need a bone, simply the OCL offset x=0 y=0 z=0 (dead center of your models.
now if you dont give the crate a model(physically) it wont even show, but still do its thing.