The thing is that approach is inherently much more effort and riskier. Also conditional on controlling the knight rush, by mid castle age knights are not really a problem.
At a bare minimum stone walls are almost universally available and solve a lot of problems knights pose and by mid castle age there’s been quite a bit of time to get the defenses up. Camels, many UUs, and infantry civ milita + pike compositions will also keep knights in check. Elephants would keep knights in check if they weren’t so easy to avoid by knights, easy to see coming via scouting and so hard countered by pikes before mass + blast damage can effect an advantage. For players who practice with monks they’ve gotten enough time to get a complement to the monks up.
The problem is on average knights are so powerful in the first half of castle age that players are put on the back foot which renders the relations above moot because the conditional of “controlling the knight rush” is hard to meet. Importantly knights provide a straightforward and profitable strategy profile. Namely if you see someone investing into spears and walls, just skip the knights and boom and win 10 min later based on the raw differential in economic power. If you don’t see them investing into spears and walls just take advantage of the startup cost asymmetry and get a good first raid in. For a huge range of elos this is an extremely profitable strategy profile. The scouting asymmetry caused by a defensive opening also feeds into this.
As far as I can tell the problem has always been the rush not the unit itself. It’s why Franks, whose only real knight benefit is the streamlined nature of their opening, are the main problematic civ. Other civs contribute but to a lesser degree because they can’t take advantage of the rush as much. Adding a new unit would only fix the problem if it had a transition dynamic that pikes lack. But since that’s the case, why not change the transition dynamics of pikes directly? It’s cheaper, faster, safer, and a better understood problem which makes feedback easier to incorporate.
E.g. Let’s trace out pikes +1 cavalry attack. This is a small change on a well known existing unit. I invite you to compare this analysis with designing an entire new unit (as well as the dev’s track record on convergence time for new unit balance).
The side effects, if any exist, will require a change on the non-pike unit or an acceptance that the change is a beneficial side effect. At the end if the list of side effects is small or at least not prohibitive enough to prevent the change we can change it. First thing first, subtract one elephant damage to compensate and keep that the same.
We already know +1 cav attack doesn’t affect bloodlines knights directly, it just changes the sensitivity to upgrades. However non-bloodlines knights will die 1 hit faster when upgrades are equal. Bohemians, Britons, Burgundians, Byzantines, Celts, Ethiopians, Koreans, Malay, Vikings. Literally all of these civs have very strong anti-pike units, rarely feel a need to use knights, or like Malay and Burgundians the change is moot because of civ bonuses. So things are ok there.
The change to pikes will have side effects on light cav with bloodlines which can be accepted or compensated for with 1 cav armour for light cav (which is back to 0 on hussar). The only real risk for adding 1 cav armour to light cav is eagle vs light cav as any other anti-cav unit thrashes light cav already so much 1 extra armour won’t really matter. This will make eagles vs light cav a relatively close fight. I think this is an acceptable side effect but you may disagree. Either way this is fine.
Lancers have the same problem light cav does but luckily only cuman lancers have the problem after upgrades. Cuman lancers probably need a buff anyway so that can be handled separately. Acceptable. Shrivamshas are unaffected in any appreciable sense.
Cav archers are unaffected in castle age but a slight buff for pikes in this relation is not really a problem anyway. Now we go through the UUs which are assumed to have bloodlines if available. Remember pikes can have anywhere from -2 to +2 attack depending on relative upgrades.
- Ratha. Takes a nerf when pikes have +0 attack (# of cav armour = # of infantry attack). Can be granted 1 cav armour as it underperforms anyway or left alone.
- Konniks see the exact same changes as bloodlines knights. I.e. at -1 pike attack hits to kill changes from 6 to 5.
- Coustillier. No effect except when pikes have -2 attack. Moot.
- Cataphract. Can give the unit +1 cav armour. It already negates all castle age anti-cav except pikes. Effect in imp is negligible.
- Tarkan. No effect except when pikes have -2 attack. Moot.
- War Wagon. No change except at -2 attack. Moot.
- Leitis. Same as tarkan. Fine.
- Magyar Huszar no effect at all.
- Mameluke. Reduce pike mameluke attack by 1 for no effect at all.
- Boyar. Not effect except at +1 pike attack. Bit of a downside but acceptable.
- Keshik. Takes 1 less hit to kill when upgrades are equal. Definitely a downside but it’s primarily an anti-archer unit so acceptable.
Unless I’m mistaken that’s everything. As far as I can tell the side effects are not problematic. But this is one minor change. Developing a new unit is much harder.