Here is an idea that I don't think anyone has thought of yet... A grappling hook. All you have to do is make a script that makes it so that when your soldier is near a building or other static object, he gets a new action "throw grappling hook". When this is selected a rope appears from the top of the building down to the soldier's feet. You would then be able to climb up it like a normal ladder. It could even be incorporated into ECP to equip all spec ops.