FrogReaver
The most respectful and polite poster ever
I think this is a pretty interesting idea. To make it really work, I think you're going to want to pre-prepare some logistics numbers, like how much you need to feed your workers per day, how much you pay them, travel times etc. You'll also want to have some numbers for how much a man can dig per day etc etc.
I don't think you need to formalize mechanics for workers dying or revolting or stuff like that - think of those as 'encounters' that need to be solved by the adventurers.
Personally I'm now intending to incorporate something like this into my own campaign: I'll make it really clear that there are large sections of dungeon that are inaccessible due to mundane concerns, along with extremely large, valuable items that require a lot of manpower to shift. I'll also make sure the PCs encounter some sort of labor representative. I think they're smart enough to put two and two together, and I make sure that gold is free-flowing enough that they'll have the funds to do this sort of thing.
I think the main difficulty is doing this early enough that the challenges introduced can't simply be magicked away, while still making the quantity of manpower required small enough to be believable.
Was on iphone earlier. I think you make excellent points. Certain things need fleshed out regarding the workers. I think this can be done on an expedition by expedition basis instead of having global rates for the workers that affect all expeditions. Though eventually hammering out some baseline suggestions may become important.
The great thing about magic is that if you simply disallow long rests while on the expedition or make long rests nearly impossible or very dangerous (which in such a setting would not be hard to do) then you can at least contain long rests and magic recharge rates. My basic solution would be to change long rest to 1 week and short rest to an 8 hour rest. This means that in order to get a long rest the party would need waste a ton of time and resources that they may not have to waste especially when accounting for the workers needs.