lurker's comment:
How big do you plan your cities to be? If more than 12, well, you will need hospitals to do that, and they don't come early.
If you plan to max out at city size 12, then what you plan is rather easy and efficient. If you plan to grow larger than that and work all 21 tiles of a city, then this plan has a problem, since many workable tiles will not be worked for two ages. In this case, plan your core cities, but until you get hospitals build some cities-to-abandon that will let you work the tiles between the 'real' core cities.
Uh, I have heard this talked about but have yet to see it done in a game. It might be helpful to gives those cities-to-be-disbanded a special name even something as dull as 'Disband01'.