I thought it was agreed that pikes have unnaturally low recruitment costs to begin with (around the cost of peasants), so the idea that halberds have to beat them simply because they cost more goes out the window. You should just bump the costs of pikemen up to match their abilities, rather than attempt mathematical gymnastics trying to make performance match cost.

The cheaper cost of pikes is offset by a MUCH greater investment to build them in the first place, plus they have an upkeep cost competitive with most other units. It's only the recruitment cost that is anomalous, so I suggest you try and balance that rather than unit stats.

I have no problem with halberds being competitive with pikes, but to make them beat pikes senseless? That's more than a little counter-intuitive. You say it's not fair for Poland and Hungary etc to have their last-tier infantry so weak, but what about all the other factions that have to scrape to get pikes, only to see them defeated by a lower-tier unit with superhuman stats? They are both infantry equipped with long weapons, there's no call for one type to be very hardy, have more armor than DGK and higher defense skill than virtually any other spear-equipped unit in the game, plus having an AP attack comparable to 2handed swordsmen.

The radical changes required to make any unit even survive against fixed pikes from the front just confirms my view that pikes are really unsuitable as a unit type to be balanced against in the first place, always assuming that they are not meant to be the ultimate heavy infantry (with significant drawbacks such as speed and facing to limit their effectiveness). Jacking up a lower-tier, hybrid unit specifically to mash them, just to benefit two factions whose advantage isn't even in infantry to begin with, may be a little too much.