I've come across certain situations where my crew were often low in health and I required them to, you know, remain alive; while I happened to have almost full health due to attacking far away (us Witchdoctors tend to do that) or the enemy has decided to attack the crew more often than moi.
The "ability" (I am unsure if this is the correct term) would work for one round and would direct this rounds' attack(s) at you as the Captain, mainly because the Captain usually has a higher health capacity and because it would feel odd to direct an onslaught of attacks onto another crew-mate (apologies, Mormo). It sounds like an odd idea, but I think it would be useful in particular situations, especially if your crew is suffering while you have near-full health and could take damage to your health.
Flaws to be considered: 1. You would likely have to be at a certain position for it to work, depending on the attacks of the enemies (perhaps there would be a range limit). 2. Possibly it would take off too much of the Captain's health, depending on the enemy(s), so maybe rather than taking full damage it halves each attack (which, if the ability can be upgraded, increases as it gets more powerful: e.g. takes off 75% of each attacks' damage). 3. It would only be useful in that situation, so it may not be used a lot.
Just an idea; I'm sure there are more flaws with it, but I thought it might be an interesting ability.