Luna might be interested. She doesn't have any experience with filial magic, but she is a magic user of sorts, and I don't think it'd be unreasonable for Luna to try her hand (hoof) at advising other people/creatures with learning their own sorts of magic or trying to learn filial magic herself. (And then she just has a general interest in other magics/cultures.)

As for the joint projects idea, I've toned her powers down a bit, and her magic works best at night/during a full moon, but she's able to minimally alter local weather and can levitate/transform objects/create illusions. Ponies have also been known to create barriers (like, around a whole castle/city...though not Luna specifically).

If any of that sounds useful. I can't think of any concrete goals for the moment, though.