Seeing as Brightsteel is not Breedable, I'm going with Goodwitch/Metal. Finally just got my Goodwitch today sitting in the Nest!! But Breeding Possiblilities went up for it with the Introduction of Hippogriff Dragon, and now has 10 Breeding Possiblities now (for any who are still trying for Diamond).
Gonna be taking Advantage of the Boosted Breeding Weekend and gonna Try for Diamond just as soon as she can Evolve to Level 4!!
Wish me Luck guys!!