Horse - Roll 2D6 in combat. If they have Impetus then add extra one hit if the dice score a double. Lose Impetus if either die scores a '1'. Move 10", but can move 12" if this allows them to contact an enemy unit.
Dashing Horse - Roll 2D6 in combat. If they roll a double then they score an extra hit, but take a hit themselves. If they destroy the unit they are fighting then they take a hit (but they don't take two hits if they roll a double as well). Move 10", but can move 12" if this allows them to contact an enemy unit.
Disciplined Horse - Roll 2D6 in combat. If they have Impetus then add one hit if the dice score a double. Lose Impetus if either die scores a '1'. If they currently do not have Impetus then they regain it if either die scores a '6'. Always move 10".
So basic Horse are assumed to have a certain level of impetus which they can lose and never regain. Dashing Horse never lose impetus, but become disorganised by their own combat actions. Disciplined Horse do not get to charge into combat, but may reform, getting their impetus back. Obviously Dashing Horse can represent Rupert's Royalist cavalry, whilst Disciplined Horse can represent armoured Lobsters or later Parliamentarian cavalry. I have left whether the horse are fighting with sword or pistol as their primary army as an abstract.
I am now working on three grades for Pike and Shot - Balanced, Pike-Heavy and Shot-Heavy. Balanced Pike and Shot fight with 2D6 when shooting or in close combat. Pike-Heavy foot also roll 2D6, but get an extra hit if they score a double in close combat, and score one less hit if they score a double when shooting. Shot-Heavy foot reverse this; one extra hit on a double when shooting and one less in close combat.