Isn't trek always officer-heavy? I think O'brien is the only NCO in the fleet...
By "nowhere to be promoted to" I was thinking specficially that Janeway can't promote herself or elevate chakotay to her own rank.
More generally, there's the problem of lack of new job openings (unless someone gets killed) and there are limits to how far you can promote people when they're still in the post they held at launch.
But I'd have thought harry could have climbed one measly rank on the ladder, in recognition of his years service. Also, I mean, he's got a full-time bridge post and he sits in on command meetings. Unlike all the other Ensign Joneses that are working in engineering or laundry department or whatever. So he's already more accomplished than them. Think that justifies a pip on his collar.