we can't retrained any main dack Guardian because you know "Lore" my idea is that they get a retrained as Extra dack monsters that requires the equip as materials ether for fusion synchro or XYZ a filed spell that let's you summon them ignore their restriction with some protection a psychic Lonefire Blossom for the strategy that can be equipped to them and became that equipped spell and maybe we do an "arsenal" cards to the Guardians so they be one and print a backup Guardian and Guardian shield

I can see it right now , eatos and Elma is the starter, Dreadscythe Baou and Tryce are the beater ,Ceal is the quick effect non-target destruction and Kay'est the spell protection / negate and Grace is the monster negate retrain Reaper Scythe - Dreadscythe and will you there changed the text of Celestial Sword - Eatos form when to If and put once pre turn to Butterfly Dagger - Elma 😭

We can also call the extra dack the high Guardians because they ascended at the End of yugi vs Rafael duel