Dann's little more than a one-note character, a punching bag for comic relief. Besides, he's down in Engineering and not a navigator (though he seems to know his way around the ship's elevator system). I'd like him to stay there, it gives more excuses for more "lower decks" action to happen down there with three of the main or recurring cast being engineers now. None of our Starfleet engineers were that lucky, and I'm sure neither he nor Yaphet are going anywhere on account of their actors' personal friendships with the showrunner.
As for the bridge, TNG got away with the loss of Geordi and then Wesley just fine, to the point that later TV incarnations ditched the dual-upfront speaking characters altogether. I'm sure some background performer will be happy to take featured BG pay to sit up front and push buttons while in center focus.
Mark
As for the bridge, TNG got away with the loss of Geordi and then Wesley just fine, to the point that later TV incarnations ditched the dual-upfront speaking characters altogether. I'm sure some background performer will be happy to take featured BG pay to sit up front and push buttons while in center focus.

Mark