This would allow us to make our own statusbars (by enabling immersive mode), Volume HUD's, Have a way of creating a sort of AOD/Lockscreen with the help of tasker, overlay the navbar to create our own navbar buttons and if you incorporate the use of swipe gestures, our own navigation homebar(pill) that we could configure to change colours based on app. We could also create our own notification banners. I'd happily donate a decent bit of money to see this happen.