Bring the Universal App Stylus support capabilities up to speed with that of the native Office apps
I use a wacom stylus with the Desktop app A LOT (Wacom Intuos with OneNote 2013 and OneNote 2016) - and it's mostly a great experience.
The Universal App for Windows 10 however is severely lacking in that department. Using the pen buttons doesn't fully work like it does in Desktop (for example, you can't lasso to select ink), the app doesn't automatically switch to pen mode when it detects a pen beings used, and the cursor doesn't represent the pen's selected color, width or strength (all features that exist in the 'native' desktop versions). Older versions of the "metro" app also had a nice floating radial menu which was very useful - can we have that back please?