This game is amazing and comes about as close to "realistic" as any game I think I've ever played. But I do have one observation about supply.
Having played several of the campaigns, including the full FIW from both sides, I'm wondering about the value of depots. It seems to me that so long as I have at least one supply wagon, I can march an army across the map, so long as I rest and replenish over the winter inside a city or fort, even a hostile one that I just captured. I've never seen the need to worry about building or capturing a depot. I know depots provide replenishment and ammo advantages, but supply wagons seem to work just as well, so long as you wait long enough for them to replenish.
I seems to me that supply wagons replenish too easily in "hostile" territory. As the English, for example, I can take an army with just one supply wagon and capture Fort Niagara, then move around the north shore of Lake Ontario, capturing forts as I go, then down the St. Lawrence all the way to Quebec - so long as I rest and replenish over the winter in the various forts and cities along the way. Even if the French move in behind me and recapture the forts and cities in my rear, my lone supply wagon somehow replenishes enough to keep me going. By the mid to late game, I usually have several supply wagons sitting around with no need to use them.
I know the game does not model a supply chain. But I'm wondering if it would make sense to limit the amount by which a supply wagon could replenish if not located in friendly territory or at a depot - for example, perhaps supply wagons not located in controlled areas or in a depot would replenish only half as much as those located in controlled areas or depots. While not exactly a supply chain, it would place greater emphasis on controlling your rear areas and building and protecting depots accessible to your front.
I'm sure there are some subtleties that I am overlooking, but my overall impression is that supply is a bit too easy and depots too unnecessary. Thoughts?