Jesus M
Without too much research, it would be easy for players looking at prices online to mistake the cards for each other, even though one version is more than double the others value
Because of this, the only cards from the Final Fantasy set in this deck as it stands are Tidus, Yunas Guardian and Yuna, Grand Summoner
(All depending on your exact deck, of course.) Keep in mind the fact that you're playing a tribal deck, and adjust your play to optimize for that
If you want some inspiration, you can read my article on how every Commander deck can use the graveyard
While this is something that every Commander deck should be prepared to do, completely invalidating what a deck is trying to do is in its own right creating a non-fun experience for at least one party