All interactions that require the top third of the display need to be brought down. I'd put good money on phone finger-fu being responsible for the majority of broken displays.

On both of them I would make better use of the multitasking screen by having notifications sat in a stack at the bottom of the screen ready to fan upwards (like they do on the iOS lockscreen) and device controls to the right of the top-most app.

On the lockscreen a swipe to the left would bring up the same device control/toggle screen.

iOS would adopt the universal 'back' gesture from Android.

When notifications arrive they would pop up at the bottom, shrinking the app in use slightly at the same time like the Palm Pre did.

Developers would be required to make the same ergonomic changes. I actually wrote a whole piece about it here: https://carlst-james.medium.com/ergonomorphism-next-big-thing-in-ux-f895495051ed