App Launcher on prem
Bring the App launcher ribbon form O365 to on Prem and allow use to administer what icons/links appear form central admin.
This would allow the use of SharePoint as a landing page company wide with links to all corporate applications on SharePoint and external.
Philip Küsel commented
I second on this, also the SharePoint 2016 applauncher design should always(or at least be an option) be on par with O365 and On-premise.
The look of the SP 2016 on-premise app-launcher is like 2 versions behind even with the latest update (September 2016 as of now).
Exchange 2016 got the visual update in one of the later updates, but SharePoint has the oldest one.
If your going hybrid road I think it's crucial that the navigation should stay the same regardless if you are in O365 or on-premise SharePoint.
Not only for causing confusion for the user, but the UX as a whole.
To provide some further clarification: The app launcher synchronization feature is great for hybrid scenarios, but it would be even better if all of the application tiles from O365 synced down to on-prem so that user experience was even more fluid.