Two times now have I gotten the level specific bridge officers, and I have accepted them both. But none show up in Assignments. Anyone else have this?

Yes, but I gm'd it and they eventually showed up

There's a bug report about this that they want people to join if they're having the issue. Click the ? next to the minimap, select Report Bug, Missions, and the bug should be one of the ones listed in blue. Click the button at the bottom of the screen to add your name to the list of people experiencing the problem.

Cheers!