You seem to confuse interface choices as having something to do with "power". Interface choices have nothing to do with power.
- Split screen: this is already done, but on the iPad because splitting a small screen is of limited value
- PIP: this is already done, but on the iPad since having PiP on a small screen is of limited value
- HDMI support: this is practically already obsolete in the age of Airplay and Chromecast. Might as well add a VGA port. And there's always a dongle if you need one
- Multitasking: are we really still arguing about this like we're back on iOS 9? What multitasking are you doing on Android that you're not accomplishing on iOS?
- Real File Manager + Mouse/trackpad support: iOS is an OS with 2 basic underlying philosophies: a touch (finger) interface and an application-centric rather than file-centric approach. If you take either of these away you just have Mac OS X. Apple already makes plenty of devices that use OS X.
- Stylus capabilities: we know exactly how Apple feels about stylus support by how the handle the Apple Pencil: an option for special cases, not something you need everyday on your phone.
Your idea of progress for a phone is to turn it into an old laptop. Why look backwards?