Not sure if you heard but the new limited building slot mechanic sounds close to what you want?I've bought BE/RT a few days ago. One problem I think there is with the implementation of building decisions is that it seems that almost all buildings get them, within a few turns of first building them.
Not only does this cause a lot of distracting spam when I want to be concentrating on something else (and forcing me to make decisions before I really have an idea about how I want my civ to develop), it means I will presumably have exactly the same decisions to make every playthrough.
If there is something like this in Civ VI, I think it should be much more infrequent, and only affect a few (randomly chosen) buildings. So you never know what ones you will get, and if you do get one, it will be a rare bonus that will be useful to have whatever you chose. (As opposed to 'I have a choice of adding a bonus to production or something to this building. I've gone for 'production' on the dozen or so other buildings I had that option for so far, so I guess I might as well go for 'something' this time, just for variety').
For instance in an encampment you csn either build a barracks or a stable but not both forcing you to choose one. We could just do the same thing for other building quests.