Add the ability to climb on small obstacles (for example, up to shoulder height) and through large windows. Too many objects would be scalable in real life, but are not in game. Small H-barriers for example could be passed by climbing on top of them for infiltration etc.
Proposed implementation: make the "step-over-key" context sensitive, so it'll trigger step-over function before a small obstacle and climb function before a medium obstacle or window. While at it, make a soldier scale a ladder when pressing the step-over-key in front of a ladder.