Could have some combination of:
cunning/dirty fighting (obviously!)
cunning/survival
techniques/dual weapons (because cutlass+knife)
techniques/dual techniques
techniques/warcries(locked)
techniques/bloodthirst(locked)
techniques/field control (because disengage, possibly replaced wholesale by pirating/swashbuckling and/or pirating/punishment)
techniques/combat techniques (because rush)
techniques/combat training (obviously)
techniques/conditioning (because daunting presence)
cursed/fears (maybe) (locked)
As well as possible new trees:
pirating/swashbuckling (Errol Flynt stuff)
pirating/cannons (don't ask where you hide the cannon, but this could allow stuff like broadside, grapeshot, etc, a ranged tree) (locked)
pirating/pirating (because recursive, also plundering, and other nebulous pirate things)
pirating/shanties (mutually exclusive sustained effects, could be buffs, or debuff auras)
pirating/punishment (whipping, stranding, planking, keelhauling) (status effects/pushing)