I agree that this scenario is pretty unlikely; it seems at least possible if there was a high-level policy change that hadn't caught up to military funding and structure, but made active troop deployment very unlikely. Your second to last paragraph disagrees with this; does the US military really shrink that much when we have fewer wars going on?

China seems much more the model of a country with a large military that rarely is deployed, and they do seem to match your description; lots of manual labor, disaster relief, building infrastructure, etc., with less competitive pay. I agree that this is the natural balance for a country that's not engaging in wars on a regular basis.

In fact, I think that's what some of the people my age that I know in the service were expecting when they joined in peacetime. Very rare callups for crucial work they felt obligated to do well for the good of the country or world.

This might not have been true, and probably won't be true even once we get back to peace time, but if it was, it seems like a pretty good reason to join, and follows the OPs intention. Still not my recommendation!