Edit (14th January 2012): HOLY SHIT CYBUSTER GOT WHAT AND DID WHAT AND WHAT WHAT?
Edit (15th January 2012): Cleared my first playthrough. Precia route. Aces were Masaki and Ryune (didn't even upgrade anything aside from Cybuster, Valsione, and for the final stage Gino's thing's HP and armour).
Final boss. Spoilers, obviously.