Hi David -
Anyone can be added as a member of a team, so yes, it is possible to have outside stakeholders access all queues in a team.
A few others have requested the ability to share a specific queue in a team with additional people. This is not currently possible, but we've added it to the list of requested improvements to Team Queues.
In the meantime, if you only want an outside stakeholder to see only 1 queue in a team then you have a couple options:
1. Move the queue to a separate team and add the appropriate team members, including the outside stakeholder
3. Move the queue out of the Team and
share the queue using the older process.
-Cameron