Ah, by way of explanation I went with the rank of Colonel mainly because you won't find NCOs training anyone but enlisted folk at Academies. Since this is more of a ROTC environment (from what I can tell) I opted for the backstory of him being removed from the IROS Marines version of First Recon due to a mission gone wrong while acting as their handler or liaison. I haven't quite decided yet, but it will pan out and make sense.
I'm not trying to get all realistic with this, so he's going to be dialed back a bit for the sake of training students. But he'll still be an ass. :3 It should be fun, going to get campy with it.