I'm wondering if there is a convenient way to use  a single database to store my umbraco admin / editor users amongst several sites. My requirement is to allow a set of users, the same across all sites, to have certain groups of permissions. Ideally I would like to avoid having to visit each site, create a new user each time and set up their corresponding permissions.

Each site will also have seperate members.

One solution I considered was to place a client reference against each member in a shared membership database. Then create some logic to prevent the member logging in when their client code did not match a web.config client reference key.

Is there a better solution?