Admittedly I have no experience in this kind of thing, but I would have thought that the military would use people for what they trained for. If you trained for infantry, you'd do that. If you trained to work on a ship it seems wierd to use you for infantry. Would they do as good a job as people who had trained more for that?
I know when I'm at work I don't like being expected to float to an area I don't usually work in. It isn't that I think I'm better than the nurses on those units, it's that I don't feel I can do a good job there without the training those other nurses get. I do it, but I don't like it. I chose not to stay at my last hospital mainly because of that issue.