This is a follow-up to the discussion on the Google Group: https://groups.google.com/forum/#!topic/mu-discuss/APAa4rADFB4
It would be really useful to send a whole batch of messages to a single action. The obvious example is when applying a series of patches to a tree. At the moment you can to select the action for an individual message but not for a whole set. To be useful it should probably pass the whole list of message to the function so it can apply some basic filtering/sorting to ensure things are applied in the right order.
I would envision a workflow in the headers view of: T->a->g (Thread, Action, apply Git patches).
Yes, that makes sense. I'll have a look after the next release, which should be in a few weeks.