What would be ideal for LTS, is some kind of dehydrated "roux". The challenge is storing fats like oil or butter.
From there you could add whatever dehydrated veggies, like corn, onions or even a few beans. One you have the creamy soup base it could be combined with pasta (think mac and cheese or alfredo), or become the base for a chowder.
Dried pasta already stores quite well and this seems like a good pairing.
The idea of long term soup mix is a little odd, as I often make soups from left over ingredients in the kitchen.
I'd rather have LTS cans of some base ingredients, though a couple of these cans might be worth keeping.