1) Tree's, bushes, terrain in general, destructible. I agree with Karnak on that these items should stay down once destroyed until reset, but for a different reason. My reason would be is that it would give a little more immersion. That tree/barn/grain silo you shot and/or bush you ran over intentionally (or very much likely in my case, COMPLETELY by accident) 2 days ago, didn't magically go back to what it was after a little bit. It would still destroyed, and will remain so until map reset.
2) FAR more realistic road and rail networks. No random indestructible bridges. If there is a bridge, let it be for a reason (IE River, gully, etc.). No sharp turns for said road and rail as well. Connections between the towns and the fields as well as with each other EXIST, both road and rail. At the very least, a road or two that leads from the base to the town.
3) Revamp the look of the warehouse that Road Convoys and Trains come out of. Bring back the revamped warehouse that Road Convoys and Trains use to go into when delivering their supplies. Have BOTH of these destructible like the non-strat items that exist at fields, but come back up like said non-strat items. I believe their down times are a fixed 60 minutes? I've honestly forgotten. This will only be for visuals and will NOT affect game play.
4) Ports that are not half into a landmass. Terrain editor will automatically adjust so that piers and docks are actually in water. The same with bases that are half into water. Editor would automatically readjust so they would be completely on land.
5) Area's where water would be shallow, have GV's be able to go through these shallow bits. Water depth is what I'm getting at.