Danny and Spider-Man are necessarily for training Hope to control the Phoenix. And both are Avengers.
Also, we have to remember that no one knew about the Kun Lun training until Thunderer showed up... but he didn't leave Kun Lun until after the Phoenix came for Hope on the moon. So Stark and his device was really needed to delay Phoenix taking Hope and getting her enough time to get the proper training.
Lastly, we have to consider the cover for issue 12. The one with Wanda and Hope powering up Iron Man in space. I think that at least implies that Starks research (which has been a fairly significant plot point in the story) will play a role in resolving the story. And of course there's Wanda, who isn't an active Avenger but at least falls into that Avenger grouping.
Tallying up the necessary people, we've got Hope, Iron Fist, Spider-Man, Iron Man, and Wanda. Hope aside, that's a pretty Avengery group.