Well seems the concensus is to remove the bonus against gunpowder from pikes. I think I'm going to up the Pike strength to 7 though. Anyone have an issue with this? Also no new units, everything is filled out well as far as I'm concerned.
There is in standard BTS no really good counter against the cuirassier as the pikeman is just at an equal footing against it. Next to that the formation promotion (+25% against mounted units, available with combat 2) is available later than the shock promotion (+25% against melee, available with combat 1) and mounted units can get extra experience from cheap stables. So the horse units are likely to be far better promoted to beat the pikemen than the pikemen are to beat the horse units
So those are good reasons to improve the pikeman.
However, in standard BTS, the pikeman costs 60 while the knight costs 90 and the cuirassier 100. Quite a large cost difference making the pikeman pretty cost efficient if it could reliably kill knights and cuirassiers.
If you improve the pikeman against cuirassiers, then it will become very powerful against knights and knights already are not used that much because of their high cost and good counter unit (pikeman). So it's hard to balance the pikeman against both units.
You could do something like:
Make the formation promotion only available at military tradition. That could represent the strong formations that were developed for pikemen and later riflemen which were pretty effective against mounted units. Since some promotions were moved to military science in the expansion pack, this is not a weird change. The pikeman could then be strength 7 + 100% vs mounted because the knight could get a promotion vs the pikeman and the pikeman not vs the knight. When cuirassiers are developed, then the extra promotion vs mounted also becomes available making freshly promoted pikemen able to gain the promotion to beat cuirassiers.
You should maybe raise the cost for pikemen a little as they are better now when unpromoted. I'd say 65 or 70 cost.
Numbers with pikeman strength 7 + 100% vs mounted (strength ratio pikeman/horse unit):
pikeman vs knight: 14 vs 10 (ratio 1,4)
combat 1 pikeman attacking combat 1 shock knight: 7.7 vs 6,06 (ratio 1,27)
combat 1 shock knight attacking combat 1 pikeman: 11 vs 12,95 (ratio 1,18)
pikeman vs cuirassier 14 vs 12 (ratio 1,17)
combat 1 pikeman attacking combat 1 shock cuirassier: 7.7 vs 7,27 (ratio 1,06)
combat 1, shock cuirassier attacking combat 1 pikeman: 13,2 vs 12,95 (ratio 0,98)
combat 2 formation pikeman attacking combat 2 shock cuirassier 8,4 vs 6,67 (ratio 1,26)
combat 2 shock cuirassier attacking combat 2 formation pikeman 14.4 vs 15,4 (ratio 1,07)
You probably will also increase the strength rating of the landsknecht to 7. To balance the matchup landsknecht vs macemen, you'll probably will want to reduce their bonus vs melee a little. Since civilization IV seems to only have bonuses in multiples of 25%, I'd suggest reducing the bonus vs melee to 75%. That works pretty good.