Working out a combat mechanic is like cutting off the Hydra's head, each time we think we've got it nailed down, another one pops up. :-)
Ideas are good, don't get me wrong, I like ideas. Have you got a relatively simple crew-vs-crew and crew-vs-critter combat mechanic that might work for us? The only real requirement is that players can only roll one or more d6 and it should be fast and low-math.
We'll run them through some play testing and see how they work.