Highland clansmen, feudal sergeants, mounted sergeants and archers (leave the longbows at home, unless you have cash to burn) will handle any AI-controlled Muslim army, especially if you build them with full weapon/morale upgrades.

You might also want to keep a couple of feudal men at arms handy, but do try to rest them when they get too fatigued. They won't be able to engage the enemy for the full duration of the battle, rather you'll need to rest them periodically. But they're useful as a reserve and specialist element because they can outfight pretty much anything the Muslims can throw at them while they do have some strength left in them.

I recommend no armour upgrades at all, but morale and weapon if you can get them. Every point of armour is a hit to fatigue loss and recovery (and past a certain point, I believe it's 5 or 6 armour, you can't ever gain fatigue from resting - rather with these guys you just constantly lose fatigue - faster if you do anything other than stand around).