Yeah the visual feeback for the player seems to be the worst part of this game and In really need to take another look at.
I thought once about having Impassable areas but decided against them and made the soldiers go slower depending on the steepness/height of the area, which you can see on the height map.
For the guns, if you mean the artillery, you can select them first, then select a target (within it's range) and then a projectile will be shoot from it to the selected point.
I never thought about a 2 player option, one as the Austrians and the other as the Italians may be really fun.
Thanks for the Feedback :) !!