B'elana was a utilitarian promotion. She'd proven herself to Janeway that despite her discipline issues she was just a better engineering than lameboy. Also the promotion was a message to the Maquis that they are equal members of the crew.
I didn't know until recently that all human characters in Voyager were under explicit instructions to be lame.
It's true Janeway was a hypocrite in some ways but that isn't necessarily a negative for a fictional character.
I'd prefer that over Archers perpetually slightly annoyed manner of dealing with everyone and everything.