In one of my projects, we were doing something similar. But how are you handling the scenario where user authentication details have changed in Salesforce? For e.g., password has been changed in Salesforce but since the details are now stored in AEM, the login would still be successful, which is incorrect.
This was the scenario we had missed in implementation and later we had to write a sync job which updates the authentication details whenever there was any change.
We had handled Salesforce integration differently in other project (not on AEM but different CMS), where all user details were stored in LDAP instead of CMS's user management. This one definitely worked better for us but then CMS wasn't AEM.
Thanks, Dipti