The only few things I’d put on my wishlist are a mini Apple Pencil for the PM variant (if you’ve used a Samsung with the S Pen, you’ll understand that they’re pretty good to have) and the ability to do transparent widgets and remove the app labels from underneath the icons for a more clean Home Screen look.
I want to be able to put my icons wherever I want on the Home Screen, and faster charging. +1 to a flat(er) back. The way the phone sits is obnoxious especially without a case. More color options for the Pro/ Pro Max line. Double and triple press options for the action button.