Deploy them a hex or two in front of your main line and they can act as a shield.
Skirmishers are also extremely difficult to dislodge from obstructed terrain.
Formation changes attempted while enemy forces are nearby may fail. Lower-quality units cannot be expected to change formation successfully on a consistent basis in the presence of the enemy. Given the broken terrain of the Borodino battlefield and the lower quality of the troops, you will probably want to move and fight in column. Infantry in line can easily become disrupted by obstructed terrain and stacking with other types of forces. Never expect a charge to carry a prepared enemy force.