How about once you get certain city improvements, you can start having 'factory drone' city specialists who increase shield production? This could be expanded to scientists, taxmen and entertainers too. For example...
Marketplace allows you to have 1 taxman, bank allows 2 more (total 3), stock exchange allows 3 more (total 6).
Library allows you to have 1 scientist, university allows 2 more (total 3), research lab allows 3 more (total 6).
theatre allows you to have 1 entertainer, cinema allows 2 more (total 3), VR centre 3 more (total 6).
Workshop allows you to have 1 factory drone, factory allows 2 more (total 3), manufacturing plant 3 more (total 6).
This also makes these improvements more critical. A citizen who cannot find work (either in the tiles or the buildings) is essentially unemployed, and is automatically unhappy.
Marketplace allows you to have 1 taxman, bank allows 2 more (total 3), stock exchange allows 3 more (total 6).
Library allows you to have 1 scientist, university allows 2 more (total 3), research lab allows 3 more (total 6).
theatre allows you to have 1 entertainer, cinema allows 2 more (total 3), VR centre 3 more (total 6).
Workshop allows you to have 1 factory drone, factory allows 2 more (total 3), manufacturing plant 3 more (total 6).
This also makes these improvements more critical. A citizen who cannot find work (either in the tiles or the buildings) is essentially unemployed, and is automatically unhappy.