Metroid Prime 2 was excellent too, I thought, except for the sharp difficulty spike at the very end. I still managed to finish it the first time I played it.
Hiring outsiders who engage in such projects is not going to happen. I doubt they'd want every Tom, Dick and Hacker getting encouraged to try following the same path into Nintendo. Plus, you know, "not invented here". There may be some legal reasons for that philosophy. Not sure. I do know they need to protect their IP actively, or risk losing it.
Playing devil's advocate, maybe they knew about this project before, but found it impressive enough to let it come to fruition, then C&D'd it, after it was already in the wild. Satisfy legalities, let us have it unofficially. It could happen . . . maybe.