Is it possible to make changes to a Flash Report's list of recipients in Vault?
Yes, this is possible. After creating and saving a report, the report owner can manually add or remove Flash Report recipients in the Sharing Settings of the report.
After adding the desired recipients into the report's Sharing Settings, proceed to schedule a Flash Report from the Action Menu of the report. Flash Reports allow scheduling reports on a daily, weekly, or monthly basis. By default, it distributes the reports to all users, who have the correct permissions (Owner, Editor, or Viewer role) in the Sharing Settings.
Vault Reporting Documentation: Flash Reports