Ability to allow a non-admin-level admin-panel user to see trees in two or more orgs

As far as I understand (and it's been confirmed by @sebastiangaertner), a user can only be under one Org, and see only the trees of that Org, unless they are an admin. We now have a paid worker and her manager approving trees in several Orgs. It's really important for QC reasons that a user only make species IDs from their own user account. This would require adding a join table so users can be allowed to see several Orgs.