It's possible. It also explains why they neighborhoods replace farms - if you hit the cap, you don't need more food. What bothers me:
- How the game should handle the pillaging of neighborhood? Is it immediate pop drop?
- Hard population cap was an issue in earlier Civ games but was thrown away after Civ3 in favor of more dynamic systems. I'm not sure I see the real goal behind returning the system back.
A pillaged neighborhood probably you keep the pop but get a happiness penalty for being over the cap.
Suburbanites would run to the city when the army comes.
Sounds like a city would have a cap of population (lets say 10 or 12) then get like a +1 pop cap per neighborhood. India's city pop cap might be double or 150%.