This rule was originally introduced in the 2nd Edition Complete Fighter's Handbook. Warriors classes and multiclass warriors could opt to spend 2 (or 3) pips to gain proficiency in an entire group weapons (I'd suggest using the original BG1 weapon groups). In the core PNP rules, the cost was 2 point per group. They would still need spend points individually to specialize in any single weapon in a group they already have proficiency in.
Basically the happy medium between the BG1 rules, and the BG2 proficiency rules, the latter which require too much party micromanaging particularly at low levels. Would replace the current Alter Weapon Proficiency System -> BG-Style Weapon Proficiencies mod in BG2Tweaks.
