Thanks for your feedback, and yes, I also agree that adding a boolean to the divert-configis a good approach.
There is one other thing about the implementation I'm thinking about though... after the divert sends the message copy over to postOffice it passes 2 additional auto-create-checks already. They are not passing because the diverted message does not have an associated serverSession which is where the actual auto-create-check is implemented. I can add the serverSession from the original context to the message copy, and then the auto-creation works without any additional changes to the divert. I do not know if this is okay to do though or if it has any potential side effects (all divert related tests I've run passes). If this is an acceptable way of doing it, a divert-config such as "reuse-user-session" could be used to gate new vs old behavior?