I'm pretty sure hooded guy is old man Cloud Strife (a VII cameo would easily make this game reach fastest sales in the series) and we'll learn he used the Rainbow Materia to travel worlds because Sephiroth learned how to create a dream world out of the anti-Lifestream and is secretly Noctis (his comrades are his "children" from AC) who doesn't realize he is the greatest evil in Gaia. It's not actually FFXV! It's FFVII-2!

On a more serious note, I like the theory that Luna is the Dragoon and the Freya connection in the name makes the theory work for me, though it's just as likely she's a completely different character.