How about debuffing enemies? Clerics can also do the whole curse thing ... could a Captain's intimidating demeanor in battle provide morale penalties to his foes? Perhaps the Captain should get an ability that lets him use the Intimidate skill to cause a fear effect or some such.
Actually, if I was going to go all-out with this class, I'd probably create a pool of gambits he could draw from, akin to Bardic music or a Cleric's spells ... although the net result would probably end up going back to looking like the original Marshal. :D But as this is something I want to be able to easily put into E-Tools and use without a lot of headaches, I probably won't go that far.