The ride was always going to focus on Mirabel since she's the protagonist of the film and she's popular. If they made the ride about Antonio and the rest of the Madrigals are side characters in this ride, then it really doesn't work that well and it makes more sense for Mirabel to be the main character of the ride with the rest being side characters. And I'm sure Antonio will be involved in some way, sure maybe not the main character per say, but probably important like a sidekick if that makes any sense.