In DLV we have some billmen, the armored ones, using a longer hafted bill and 'spearwall'.
If you just want yours to use the same animations as halberdeers then change this;
Code:
11 MTW2_2H_Axe 0
1
19 MTW2_2H_Axe_primary 0
for this;
Code:
20 MTW2_Halberd_Primary 0
1
17 MTW2_Pike_primary 0
for the models concerned (each upgrade will have a seperate entry) in battle_models.modeldb (in the 'unit_models' folder), and then you can add the phalanx option in the EDU. If they have short bills they might appear to hit beyond the range of their weapon.