Based on past experience, the Direct Input Officers (DIO), only serve as instructors during their four year commitment. In the past, they were offered the opportunity to become Unrestricted Line Officers (URL), meaning actual Nuke officers. They would then go through the pipeline, which included all of NNPS, prototype and then assignment to a sub/carrier. I realize, according to your post, that the second part is not something that you are interested in at this time. However, I wanted to toss out the info so you can get the full picture.
GC is our resident expert in all areas officer related, so I would expect him to come in with some more specific info. From a retired Nuke, that is the Reader's Digest version

Best of luck to you.