Not near as creative as you, but here are some ideas, without details )left to you)
Ministers of x- add ideology points/ turn (lives) ; add one time boost to ideology x (retires)
Privateer promotion- upgrades current ship, Privateer Commander/Admiral (for Privateer fleets)
Commander/Admiral – upgrade current ship & either based on improved static blueprint or current tech levels, add extra experience/HP/.. or range to fleet
Workers/engineers/scientist – boos/add a planet buff ; boost planet sensor range; make a precursor component available (ship or planet) ; boost a parameter )range,mfg, mining ..) on all starbases ; a level promotion
Leaders/Admins- add a planet buff; terraform a tile
Farmer- one shot boos to food
Spy- instantly steal a tech