I wish Sunset Shimmer or Trixie had replaced Twilight, at least for the slice-of-life S4 episodes where Twilight’s princesshood is not remarked upon and opens plotholes (“Rarity Takes Manehattan”, “Bats!”, “Power Ponies”, “Daring Don’t”).
Why? Well, mostly for race-balancing purposes, but also because those two deserve more development.