It is ridiculous that we even have separate Apps between iOS and MacOS. It should all be one unified OS. Apps should be able to run on all the hardware, doing as much as the hardware allows and working within the interface of the hardware be it a MacPro, iMac, MacBook, iPhone, iPad, iPod or iWatch. Scale gracefully and automatically load only the necessary components onto the hardware as needed for a unified look, feel and operation so we always have access to our data. The more power the hardware has, the more you can do. Very basic.
While we're at it, full legacy support for past software and data is also needed.