The ability to revert to the Cubase 6 style would be nice. I have not used version 7, but I find the new flat style of colours to be very offputting.
The Reaper style of themes is probably too far for this request, but we should be able to decide on how Cubase looks, in this day and age. Getting a nice new feature should not come at the cost of visuals. A significant example of this are now the Cubase 8 buttons in the edit window do not stick out anymore.