Yes. You can have multiple fabric users in the CitizenOrg. But, it will bring no benefit because inhabitants will not update the ledger, while it will make the inhabitant-application more complicated.
We could consider the staff-application to have multiple fabric users in the CityOrg. It will enable us to track who updated the ledger and it will not make the staff-application complicated assuming that there will be only several users in the CityOrg.