i think that would be ok too, but the solution i prefer is to narrow residential street lanes (and on other urban streets as well).

all roads, but even residential streets, in car-centric cities like LA seem to be built wide enough to accommodate 747's with ease.

my proposal: rather than 12-15 foot widths, make urban residential street lanes 9 feet wide (cars are typically 6-7 feet wide, delivery trucks, 8 feet wide). replace parking lanes with slightly grade-separated (3-4 inches) bike lanes, leaving existing walkways for pedestrians only.

and make sure these narrow lanes have shoulder lane markings.

Grade separation would work in warm climates, but anywhere it may snow it is somewhat dangerous as hitting the hidden curb could send you out of control.

In one street of my city the parking was replaced with two way bicycle lanes, and there are plastic bollards to separate it from the road (which is probably around 9 feet now as you suggest). Compared to a grade separation that isn’t going to do much if you go over it, if you hit a bollard it’s going to leave a nice permanent mark on your car, so you are going to drive more carefully.

The only issue I’ve seen with this is if vehicles need to deliver to the shops and bars on this street, they have to park in the cycle lane (there is no rear access or parking).