Not a bad idea actually. If it pays for the training, go for it.
I don't have any experience as a deck officer but from what I have heard you will be proficient with most of the aviation subjects, especially law, meteorology, navigation, aeroengines etc. (As they say law of the air was derived from the law of the sea). I know a 3rd Engineer who did a few missions and then came to fly with us back in the day. He was very good at most of the subjects since he was already familiar with them.
Maybe a shippie can give you a better insight.
