The option to delete workspaces was recently changed to use archive instead. This helps to avoid mistakes in deletion as they can also be restored.
However, there is not a way to bulk archive workspaces. Doing so would be necessary in situations where a team is cleaning up their workspace hierarchy.
This should be added to the bulk edit option from a list report of workspaces.
In an ideal world, you could pick and choose which workspaces in the hierarchy will be archived with a check-box or radio button. An alternate path to accomplish a similar goal would be to give the user the option to archive all workspaces under a given workspace line.
Looking forward to seeing how you go forward with this!