I would have liked more Scarlet Witch & The Vision
Their dynamic was interesting to me, they are played by two good actors and, to be honest, the characters were intriguing because the films have underutilized them.
They have some interesting storylines in the comics. I'd be a lot more inclined to see a film focusing on an android and a former villainess on the run from the government and trying to make a life together than Ant-Man & The Wasp.