In my opinion, this class isn't very practical. The way I'm reading all of this, he's only useful when 1 or 3 other 'crew members' help him, which means unless he gets a cohort or minions of some kind there will be PCs wasting time loading the cannons turn after turn.

Oh dear. Where are the rules for a bombard, anyway?

In addition, you'll want to make the numbers on the stance/maneuver table cumulative, methinks.