Importing one dummy PST into several archives

Hi,

I have many stubbed archives left after several Vault/Exchange/AD migrations. Their indexes cannot be updated, rebuilt, granted permissions are not being applied. Also cannot see any folder's structure within. The only way to access the data is to search from EntVault service account or export to PST. 

However I've found a method to revive these archives importing dummy PST file with one test folder and message. After import they start to show all the items, can be indexed, shared, etc. 
Because I have about 500 hundreds I need to find a quicker method to re-create their structure using script/SQL Update statement than using PST Import wizard.
Do you know any methods/solutions to share with me?

Thanks
Mike