I often use the following Scottish stack, which is available fairly early:

4 highlander archers in a thin line
4 highlander nobles/order knights (border horse until nobles become available) in two groups, hidden at the flanks
6-7 highlander pikemen or scots pike militia (use ordinary highlanders until pike is available) behind the archers
4 highlanders in two groups to cover the flanks of the pikemen (later replaced by noble swordsmen).
General
1 bombard if sieging.

Not very sophisticated, but:

- Position yourself in a forest
- the archers pelt the advancing enemy and retreat behind the pikemen
- Pike holds the enemy (the militia will take huge losses if used)
- any enemies who try to flank you are dealt with by the highlanders
- pinned enemies are charged by the highlander nobles from the flank or back
- Archers are either put at the flanks for continued pelting or set to a dense formation (skirmish off) and used as an extra "charging reserve" (scottish archers are better at melee than at archery)

The general takes out enemy archers.

Obviously this setup has deficiencies on the attack (where I'd at the very least want to bring some border horse along) and would probably get eaten alive in MP, but against an advancing AI it works fine. The highlander nobles have the same charge bonus as feudal knights. I could use order knights instead of nobles, but prefer not to as I find that the lack of knights adds to the flavour of the scots.