Also would like to request some solution in an AD Connect (hybrid or non-hybrid) scenario. Typically we convert a terminated employee to a shared mailbox but that brings up an issue with the AD sync part. If you move the AD user account to a non-synced OU, then it deletes them from 365, even if they are converted to a shared mailbox. So you either need to continue syncing your disabled users or you need to jump thru a few hoops and run a powershell command to set their ImmutableID to null in order to sever the link between AD and 365. Then they can continue to exist as an "In Cloud" account.
If there was a button in this offboarding wizard to say "break the link from AD connect and leave them as a cloud shared mailbox" that would be incredibly useful!
Jason