Undo Button - It'd be really nice to have an undo function of some sort. You can cancel movements, but it's too easy to join the wrong stack or misclick somehow and lose your nice entrenchment. It's really frustrating when you're in the middle or near the end of your turn and you lose a high level entrenchment at the front somewhere. Then it's either redoing the entire turn or hoping that you're not attacked there for a couple of turns until you regain those entrenchments.
River Supply - The supply overlay is a very useful tool, but it leaves out river supply. Would it be possible to include rivers in the overlay, perhaps with a different color scheme so they're still readily apparent on the map.
Divisional Edits - The way to form and later change division makeup is a lot clunkier than it needs to be. Could we have a simple easy to use system that lets us remove and swap out elements without having to go through a whole rigamarole in splitting the entire division apart simply to pull out one component part. From my understanding, a lot of people (including myself) will form divisions up on the fly. This often results in divisions that will need to be balanced once you have the time/desired elements available. It could also leave you with a division that has open element slots but you need to pull out a single regiment or battery in order to make room. Or the division has been relegated to garrison duty somewhere and you want to strip out a brigade or two in order to send those elements to the front somewhere.
A drag and drop feature would be extremely user friendly. If you hover over the division symbol, a window pops up showing all the sub units. Perhaps clicking or double clicking on this would keep the window open and then you could pull sub units out? Or maybe an new special order in the command tent menu?