As of
this commit today, I've removed all references to the heavy skill which appear in the UI and research texts. For those who are playing a game compiled after this commit, please keep an eye out for any mentions of the heavy skill I may have missed. This doesn't include generic references, just references to the skill which is no longer used.
OK:
The machine gun is a heavy automatic assault rifle.BAD:
The machine gun requires a heavy weapons specialist.