Christian Hecht wrote:
"Units have to break down as far as possible into skirmishers when entering woods to do combat, this does not apply when the unit is only passing the wood on a pike, road or path. Skirmishers can move as usual while the parent unit can only move 1 hex."
Generally combat wasn't conducted in woods, certainly not in massive formations as it was done on the open fields, grasslands and open areas. This applies to infantry, cavalry and artillery, no matter whether they were linear, light, guard or any other unit type. Primeval forests, woods, copses, thickets, shrubs, etc. were a big problem and could even be a barrier for the movement such formations during the Napoleonic wars. They used roads, paths, gaps and glades to march into the forest but didn't march as a formed unit through such terrain.
Is the demand for a maximum breakdown and the slowing of the parent unit acceptable?
+++
Apart from I once hid an entire Division in a forest and ambushed my unsuspecting foe on the march, causing great consternation and slaughter..

"in the woods" seems to be out of era to me.
I'd allow formed infantry units, cavalry (if you must), artillery and baggage to venture into the first Hex of Woods/Forests and move or even fight in that margin. Infantry skirmishers should be allowed their usual +3 hexes further in (though I prefer a maximum +2 hex from parent distance rule for skirmishers) ... otherwise no units other than a routed unit (which would escape through whatever terrain it could) should enter a forest at all (unless on a road - and "one hex in" would mean from the road, in that case).