@jwojda I would encourage you to check out the following: https://www.jamf.com/jamf-nation/discussions/35469/apple-plans-on-removing-enterprise-options-for-ma...
As you're finding, the current delay mechanism is insufficient and is definitely not adequate for what admins need. And Apple plans on leaving us with just that as a mechanism for managing updates.
Have you guys tried jamfhelper delay.
However I m not sure to what extend it can be delayed.
/Library/Application Support/JAMF/bin/jamfHelper.app/Contents/MacOS/jamfHelper -windowType utility -description "Please restart now. -button2 "Restart" -showDelayOptions "0, 60, 180, 300" -button1 "Cancel" -cancelButton 1