In general I’m a fan of expanding the reach of regional units.
The following is more related more to Huns than Turks. I think if there was a second upgrade (third tier) of steppe lancer then it’d be easier to give certain civs (at least Huns) steppe lancers, and then cutting back on their knight-line.
Huns have paladins rn. If there was a third tier of steppe lancer then instead of giving huns paladin, they could stop at cavalier, and be given the third tier of steppe lancer.
If you give Huns steppe lancers that’s just a buff to the huns, since they’d now have an additional option. Giving them steppe lancers but removing paladin would be a big nerf. But If there was a third tier of steppe lancer then you could give that to the huns, so as not to buff or nerf them (in concept, I realize that balancing things is more difficult than “x number of upgrades therefore same”). Also giving a third tier means you can keep the second tier where it is right now and let civs like the mongols keep steppe lancers but only give them the second tier, as they don’t need a super powerful melee cavalry option. If the mongols need heavy cavalry they already have the cavalier.
Cumans might also make sense to remove paladin and give them third tier steppe lancers. I’ve seen discussion about the persians getting steppe lancer (mostly around whether the in game civ more represents the sassanids or the safavids, etc etc). I really don’t have a horse in that race (pun intended). However if you did give persians step lancers, then they too might get the third tier of steppe lancer and lose paladin.
Turks probably just the second tier. Maybe keep cavalier, IDK.
Magyars and Bulgarians, could also be argued to get the steppe lancer because of their nomadic steppe origins. Maybe just the first tier to emphasize that “origin” part.
I think that steppe lancers might also use a bit of a buff in general. I know they’re micro makes them better than their stats would suggest, but still. Maybe a third tier would be enough and you wouldn’t need to buff the first and second tier. Perhaps instead of outright increasing their stats, you gave them some attack bonuses against gates, villagers, and trade carts. Not only would that be a buff and help differentiate them from knights, but I think that’d be very flavorful.
EDIT – Maybe even an attack bonus against economic buildings (not TCs though I think). Just something to increase the raiding flavor.