For me, there are several things that are needed:
Customizable
One they need to allow for more options on user customization. Resolution for instance, I like the iPad pro resolution on my iPad Air 2. And the number of icons on the home screen of the iPad is just not optimal at all for productivity. Same with the multitasking/split view panel, I have to scroll through 30 apps, 4 at a time, to find what I need. They can easily fit a 3x10 set of icons in that pane without the waste of space.
Better multitasking
Also the ability to run more than one app at the same time. I found myself needing two instances of pages open. Of course they are workarounds, such as getting ms word and pages, but the fact that we need a workaround for something so simple is just too much of a compromise when I could just use a Mac. I would really love to see them implement a windowed system, allowing for multiple apps to be open side by side, and their sizes customizable.
Desktop class software
I would really appreciate a 3D CAD creating app on iOS, specifically solidworks. But solidworks still refuses to even port to the Mac... So hopefully catia or some other company makes that move for us engineers who do a lot of 3D CAD.
More accessibility to stock apps/files
Also, if they force us to keep stock apps, they could give us the option to "open in" those stock apps. Specifically "music" and "videos". The only way to get files in there is through iTunes purchase or iTunes sync. A full file system, where all the "music" and "video" files at accessible, and I can copy and paste the files into those directories, would be a huge plus.
Don't force the use of apps
And I'm a fan of YouTube inside safari, and I don't appreciate being peer pressured into opening a YouTube app that doesn't have split screen or pip when I could more effectively use it in safari.
Primary device vs auxiliary device
I'm still facing scenarios where I need to hook up my iPad to my MacBook to do things for my iPad (iTunes sync, backups, jailbreaks, bricked restore, etc.) where as on the Mac, I never have to connect it to anything to fix it. It's got it's recovery built in to the system. So I can never really get rid of my computer, because as long as I have the iPad, I'll need a device that can repair it.