Here is a nice Halberd for "fixing" the mercenaries without changing anything in the Frozen Horror and other placed where the Halberied exists.
Halberd2.png
I've made this weapon with this rationale: it costs the same as a crossbow, because the Halberdier and the Crossbowman have the same price.
The crossbow is useful in a not crowded battle scene (or in a corridor), but the Halberd can be useful in a more tight scene (if a monster is in a corridor meelee with someone, the halberdier just in the square before is like having another attack with 2 dice: sometimes can be useful, without ruining the balance of the game).
And, the nice thing is, giving this weapon, you don't have to "modify" any rule as printed: the Halberdier cards and the Quest book rules have all in them. The only thing "missing" in both would be a "see armory", but better this than other edits or nerfs. Hope you like it!
EDIT: I've made another version of the card: now it costs like the crossbow and the longsword, but explicitily tells that you can not use a shield. So, you have to choice when shopping in the armory if you want a longsword (8 squares, adjacent and diagonal) and shield, or the halberd with 12 squares but no possibility of shield. Also, same price between crossbow and halberd means same price of mercenaries.
The old one:
Halberd.png
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