And if memory serves, you can Vanish+Doom Doomgaze/Deathguise without any negative side effects, but Vanish+Xzoning him will prevent him from dropping the Bahamut magicite.
I believe that's how it works.

I like to get the sword, because you can learn Ultima via Paladin's Shield which isn't THAT much of a pain to uncurse. I've fought in the Dinosaur forest with the Cursed Shield and the Ribbon and had no problems beating the enemies before time ran out.