@dansup yeah, multi-tenancy can be a pain to retrofit. If you know ahead of time, that you want it, you can scope the data stores to individual users.
One way to deal with it (if you want suggestions, otherwise sorry!) is to use a global singleton for storing active user ID and a factory that returns indivual data stores for each user ID and use that when injecting the data stores and changing the active account. Would that be feasible in your situation?