Agreed on the army-stealth thing. I really like having the option of pulling a Hannibal Barca and invading Italy. I also wouldn't at all mind a sort of supply-line system where you can be in, say, different logistics stances or something. Your faction may influence how your army deals with logistics, but the commander has the final say. Perhaps you have all of your soldiers carry their own gear and additional stuff, much like the Romans did after the Marian reforms. You might also go with the sort of traditional supply train thing where you also have camp-followers and whatnot. I feel like you should also be able to procure supplies in the field, perhaps by doing small-scale raids or through foraging. This would seriously aid your soldiers, provide a morale boost, make them march faster, etc. You might not even worry about bringing much food, if you go out purely to raid. Additionally, you ought to be able to get food from a defeated army, if it works with a supply train and didnt tactically withdraw.
But yeah. Logistics should be important, but not altogether necessary. There should be nothing wrong with just piling food into your inventory (which takes up valuable loot space), but there should also be better options, each with their own drawbacks. Having your soldiers carry their own food may require better foraging and procurement, and thus make you need to send soldiers to go and find food for everyone else. Supply lines may be able to get raided or cut off if you don't invest in protecting them. Raiding is risky as it takes lots of time and makes people really hate you. You may even get tribute from surrounding areas, if you establish a more permanent fortification. This may, however, impoverish the surrounding areas, slightly.
Or you could use airplanes, I don't know. That stuff would be vulnerable to anti-air batteries. Then you'd have to get mechanized infantry and tanks to support them and..
Wait we're in modern era, right?