I've already submitted this one to Apple - but the really obvious one for me is to auto-prominent the haptics.
People complain about the haptic notifications being hit and miss. I've noticed it's *only* when I'm up and about - never when I'm sat down. It's consistently possible to miss normal taps when you're moving your arm about.
Rather than setting it to 'prominent' all the time - if you have a notification due and you're in a busy / noisy environment (sound, vibration, movement, exercising) - automatically turn up the dial on the taptic engine to make sure you get the prod.
If you're sat in a meeting - quiet, no movement - the notification can be a normal one.