Since iOS 11 is likely to be previewed in just a couple of months, do you mean what would we like to see in iOS 11? Because I think that iOS 10 is pretty much done for new features at this point.
My wish list always starts with better notification options. I want the ability to choose which sound I want for which app, and whether I want sound, vibration, sound and vibration, or neither, for each and every notification and app. I hate the fact that I must have notification sound turned on to get a vibration notification for the ESPN app, just as an example, and have to listen to the stupid sound that they use, when what I want is just a vibration for ESPN notifications, while I continue to get sounds for Google InBox, Messages, phone calls, voice mails, etc.
Snoozing notifications would be great as well. Notify me of this in an hour rather than just clear it or leave it.