Okay, turning the random battleship Yamato insert into a relevant plot point is good. That said, there's no justification that SUPERIOR NIPPONESE WW2 BATTLESHIP would be of any use against a dude who can just destroy the whole planet at once.
Is there gonna be an asspull of anti-mage rounds that they fire from Yamato which have no limit to their anti-magic capabilities? Would invalidate the whole purpose of magic, but with this dude "creating" his own magic and whatnot they've already invalidated everything about magic that has shown up previously (the level caps, the magic massages, etc) so why not I guess...