discuss.answer
dashboards are bound to the users primary-group.
By default there is no way to load other dashboards.
Might be possible to create a custom - welcome.class.php within a custom-manager-theme and modify or extend the process-method.
As said, I think with a custom manager-theme, where you have only a custom welcome.class.php in which you load another dashboard-object into
this.dashboard in your process-method, depending on a request-param, it could be made possible.