I have a few problems with the Brave = Bravely Default rep connection mostly being that it's too obvious which a good codename shouldn't be.
You could argue that Piranha Plant's codename is obvious cause it indeed is but if we consider the "Piranha Plant was going to be in base" theory it would make sense why it was obvious as it might've been an afterthought,
Though for Joker's codename it was only obvious in hindsight since we had the character revealed to us before we learned of his codename. Some people could've thought Jack meant Jak & Daxter, Raiden, Handsome Jack, etc. but now that Joker was revealed first we don't have that so in hindsight is it only obvious.
That's one of the few problems I have with Brave being Erdrick too, it's kind of obvious.