I’m hesitant to speak much on this, because the documentation doesn’t seem to make clear yet what the separations are between sites, but perhaps the Multi Site Manager add-on could be an approach to this problem? Real-EE’ers will have to say.
In principle, I think you want some clear separation of roles, when a person can be one or another in a system, and those roles have quite different views.
If I understand it, MSM sites have a truly common user database among all the sites. So that’s handy, given you can also add custom fields to the user table(s) that could be used from their appropriate roles.
For the user with more than one role, it would matter then which apparent website they logged into, with their same identity.
One important point among many is whether the MSM can support more than one concurrent login from a given browser: are cookies etc. kept separate?
Again, Ellis folks will have to say whether it’s their intention that the MSM add-on should solve this kind of case.
Kind regards, and interested too,
Clive