There in lies the problem. Once you add pikemen and the special rules for them, everyone is going to want special rules for the formations and weapons they like. Special rules for maces and blunt weapons against heavy armour vs the in effectiveness of swords against the same etc.
Well, then, why not simply give them a broad name? Instead of pikes, maybe they use glaives, volgues, halberds, bardiches, etc.? We could call them, I don't know, poleaxemen.
