There is already a feature request for this. Details:
#23331 : Adhoc Task - configuring a completion email for an ad-hoc task.
The above feature request is for triggering an email when task is done. There are a couple of other enhancements in the works for other emails / actions related to ad hoc tasks. However #23331 seems appropriate to what Shane is asking for.
Note that the above feature request is currently being targeted for the RIO product release later this year. It has also bee