Hi,
I'd encountered a similar scenario a while ago and was able to get through it by doing the following in the admin console of Analytics:
1) Change the email address on the old employee's account to one that has not yet added in the system.
2) Reset the password for the new user.
3) Have them login and share the dashboard with the appropiraite set of people.
Of course this was before the new integration with Adobe ID took place hence would request to check if this still works and revert in case of any issues.
Thanks
Nikhil