Make the heavy lance be a 3 slot weapon
BAM
Now they can't be 1hand/shielders or top tier polearms + lancers. The heavy lance is very comparable to a pike, except usually doing way more damage every round, so a similar 3 slot penalty would be consistent and tone down the power of cookie cutter lancer/infantry builds spawning with all they need.
No need to grief a ton of classes that are relatively weak in comparison to the heavy lancer/melee hybrid. Tweak "cav" with a scalpel not a butcher's knife to anyone with riding skill.
Pretty much any melee class has a good chance against 1hand or 2hand cav, no one except long spears or pikes can typically take on a lancer. The lances with insta kill couch abilities, shield busting, and being such effective anti cav/anti all infantry weapons that do insane damage should be adjusted first.
Horse archers and horse xbows have pretty shitty builds to begin with, getting athletics or spare WPF on them is a luxury and shouldn't be punished more.