Suggestion even before I see it
Keep the W7 interface, keep a reasonable 3d theme, (do not add those damned flat and very white interface themes), mix in the W10 Kernel and voila you have won my heart...
We do not need interface changes, they already work and we know how to use them, changing the engine is fine as long as it doesn't break things. We don't need cloudy, cloudy, shiny, shiny either, honestly we don't, as an option Ok why not, as the default definately not.
I am happy with a mouse and keyboard, they work just fine. You can add the touchy feely interface but please make it optional, unless on a tablet or phone. We also don't mind if the interfaces are different between desktops, tablet and phone, its Ok, we are intelligent enough to deal with it.
And FFS leave the Server interfaces completely alone..... I want consistency between servers interfaces, the alternative means lost time trying to find the same things that I have been doing for years and no added benefit.