Hmm... I don't know if anyone has mentioned this, but what about having 2 decks of cards? Much like how AST has 2 Sect stances, why not there being 2 Card Decks? So you have Deck 1 being the old card system from Stormblood, and Deck 2 the current card system now in Shadowbringers.

Perhaps the devs could comply by giving both old and new card system and the player can choose between which card system they want to play with. Then maybe everyone is happy hopefully? So 2 new abilities given that allows the AST to switch their card system decks.

Storm Deck, and Shadow Deck