Both are interesting, I'm reconsidering citizen units continously because I agree that it has too much micro-management. But, I think that there needs to be a better way to show what tiles are worked if the current system still goes.
Old World has a system
here that involves unused citizens building specialised improvements as a one-off action.
Perhaps, each citizen is a unit with one build charge and can't ever destroy improvements. These citizen units are created like how population is grown right now. Their one build charge is used to build an improvement which they work for the rest of the game, unless it's destroyed in some way, and only improvements can be worked in a city. This way, we can show what tiles are being worked just by seeing what tiles are developed. Citizens might be reinvested into existing improvements to improve their yields or create new districts where they can then be used to build buildings.
I've got work to do, but if anyone else can follow on or give some other ideas, please do