Chris
You can compose a script (or batch job) in ETL in such a way...
- It should kill any sessions (User ID) that hits the ETL database during midnight till 5 AM. In this case, even if the user tries to refresh or schedule any report, it will fail automatically.
- It should allow your service accounts to perform its operation (BO Service account \ Account that will be used for scheduling). This action will help you in allowing the instances that were running or about to complete by 5'0 clock.
Overall, the batch job should kill all the sessions in the DB apart from the service account sessions btw midnight till 5 AM and you don't have to stop the job servers everytime.
You can also hold this batch job to allow the users to refresh the reports, if incase the ETL loads completes before 5 AM.
Hope this help you!!
~VJ