First THANK YOU for serving our great nation and from Boston, Massachusetts. I do know of a Marine that wore a Desert Camo kilt while stationed in Iraq. Second: I do not think anyone will really want to challenge any Marine, in combat gear, civvies, or kilted. Period. There are allied units serving in Iraq kilted. It would surely be a military appearance ( see the history of the kilt.). Put it on. If the command frowns on it, then put it away until stateside. I highly doubt that there would be objections from the higher ups. But then my experience was a long time ago.
Steve , veteran U.S.A.F. 1974 - 1978 . ( three months at Camp Lejeune)