Just so you know you can directly touch and slide both volume and brightness buttons (Without lifting your finger to tap again), so still just one touch. On the other features, I agree, but I really think they can still be solved by software. Basically it needs a ground up rework like they did with Apple Watch.

Keep the ability for apps to take over the bar, but also give the ability to install as a new "system" action that is always visible. Currently there is only one "app" system slot on the bar and it gets taken by iTunes or Xcode.