It would be possible to make interchangeable objects by putting them in separate gmfs and using the addXtra command in the py (this is how the practice arena works).
You would need to delete the fridge from the arena gmf first. Then shift the mesh of the alternate drops up, since objects always get added at (0,0,0). And finally make a randomizer in the py that selects one drop at the start of the match and puts it in the arena.
I don't have time to do it right now, just saying it's possible.