That can't work unless you include a 'maphack' ability with retreat. You knew the center of the map had high troop concentrations, but if they are in the fog of war, the retreat system would need a map-hack to calculate the safest route.
If the retreat system got this map-hack, you could never cut-off the enemy retreat path with a flanking squad because the enemy will always avoid your flank even though he hasn't seen it.
Without the map-hack you would just get real silly retreat paths that are not safer than we have now and will only be less predictable for either player.
So with this in mind, I would like to keep the retreat system as it is now.
+1, working as intended.