So it would be pretty cool if there was a house/apartment NPC you could add that you could play triple triad against, and at every weekly reset SE changed the NPC cards and rules, and there's a low chance to attain any card in the game.

Alternatively and perhaps easier, the NPC could clone a random NPC's cards/rules/rewards every week.

Though I do like the idea of an NPC even if only available at the gold saucer that has a low chance to randomly award dropped cards. I don't think of it as being very game breaking, because due to it being entirely random nobody can use the NPC to target specific dropped cards.