Well I was just thinking it would be less impact to simply return the new object, using a Promise or not, and leave it up to the caller to customize.

I anticipated a Promise as that does a better job exposing asynchronous errors that could result when creating new content in the future that's subject to remote failure.

Anyway, we could certainly add a content preparation/init method. Delegation would make sense but so far this would be the only delegate-able API on the rangeController.

If added it would mean that returning the object would only be for reporting success/failure and giving a reference for the new object to the caller, not for customization; the return would be for the prepared object.