Yuna is great in the 99, thats for sure but Tidus is the better Commander
It may not be a simple case of summon and challenge, but rather collect, summon, buff, challenge, and recover
Then finish with a wincon on the fourth turn when you shoot each foe for damage equal to your total costs of your stuff, save this
The Sapphire/Steel deck accelerates resources to cheat out big characters early, the Emerald/Ruby deck had lots of character removal and ways to steal Lore from the opponent, and the Amber/Amethyst deck had lots of card draw and could pull off many tricks and combos
Then you just cant interact. Miller joined the project about six months in, and says it took about another six months to reach a gameplay loop that the team felt comfortable with
Meanwhile, the sets Amber and Ruby deck contains a far more motley crew led by Tigger, In The Crows Nest