Units should consume goods

From a realism perspective you are probably right.

From a gameplay perspective, goods are already one of the scarcest resources, especially early in the game, and it would unbalance the game to tax them even further.

i would like to add to this idea, that oil or grain shortage should hit units as well, not only moral.

Imagine the situation as 2 coalitions are fighting with each other. Coalition A has a member, which lost almost all territory, but his army is full, without any harm. He has heavy shortage in grain and oil, but he does not care, as he has none or only limited nr. Of provinces, with almost zero production. Moreover coalition partners transfer their units to this member, so their grain and oil consumption goes down.

I would suggest in case of

- grain or manpower shortage each hour should cause 0,5% damage to each units.

- oil shortage air units should stay on ground, naval and land units cannot move or only with 25% of its normal speed.