9. Kill Off Ghost
Ok, so let me preface this by saying that Ghost's character worked well as a sympathetic antagonist in the sequel, in no doubt helped by the solid performance from Hannah John-Kamen. But unfortunately, she was not given enough depth to make her presence truly memorable, instead falling by the wayside and joining many other MCU villains in the mediocre category.
Given the mid-credits scene in Ant-Man And The Wasp, and the events in Avengers: Endgame, her fate still hangs in the balance, depending on which half of Thanos' snap she landed on.
If she did get snapped out of existence, then she would've returned fine along with the Pyms. However, if she didn't, that throws up an intriguing scenario, as she still needs Quantum Realm Particles to keep her alive but no one is left to help her retrieve them (unless Bill Foster also survived, but even that might not be enough), meaning that she would've probably died by the time everyone got brought back.
While being able to explore her character further via the first option might not necessarily be a bad thing, the filmmakers might be missing out on an opportunity for a serious dramatic beat if they do so.