I wish there was a way to incorporate the affects of roads and bridges, even other terrain types, on ground vehicle movement. Aside from water, there's no terrain type that has any specific impact on vehicle speed. I'd like to see movement penalties attached to different terrain tiles, along with rivers and ravines with destroyable bridges over them. Finally, I'd like to see roads crisscrossing the maps, with a positive effect on vehicle max speeds. For instance, you might have an area of marshland between a base and an enemy spawn point, but with a road running across it. Stay on the road, and you run at full road-speed; get off the map and slow (or even get bogged down completely). Or maybe the ground is smooth and hard, great for tanks, but with a river or impassible ravine cutting across the route. The only quick way across is a bridge, but one that is vulnerable to destruction. It would have a natural down time, but you could speed up the bridge rebuild by bringing up bridge construction materials via M3s and C-47s.