Hm. If Kain was in Cecil's position, he wouldn't be the one to betray them, BUT...what if he failed where Cecil succeeded? Him not becoming a Paladin (or Holy Dragoon, whatever) when they need one would definitely change things for the worse, and could be why they failed. Just a thought.

Rydia couldn't possibly remain a summoner with the change in role, but I can see her as a white mage. She would still have to wear all gear because she's RYDIA, but considering Rosa wore PURPLE UNDERWEAR ON THE OUTSIDE, I don't think Baron is too picky about fashion.