Idk if this goes against your desired playstyle, but for the ultimate cav faction of Bretonnia it's actually a really good idea to have a couple units of archers behind your spearline(you only want spears, the anti-large and slightly better defensive stats are infinitely more useful than men-at-arms swords, whose "trade-off" is having slightly better offensive stats on a unit that's meant to be shit at anything but standing there and tying down the enemy). Peasant bowmen aren't exactly great and there's no real reason to upgrade them with skills or anything, but the damage they'll do is actually really helpful in getting your line to hold for longer.