I like the idea and it is common in popular tweening engines. I also was missing a multi porperty solution so I made the extension setElementProperties (plural):
This extension could just be modifies to use a time out to trigger an onCompleteHandler.
BTW modifying the runtime is not a good idea as you will be reapplying your "patches" on every update of Hype and potentially every export of your project (depending how you set it up).