Ability to create custom debugger visualizer (DialogDebuggerVisualizer & IDialogVisualizerService) for UWP
Writing custom debugger visualizers is very great for framework makers.
But when developping a framework for UWP and Xamarin, it would be even more useful because it's often on small devices with little or no screens at all (for IoT by example).
Having a way to create custom visualizers would be very great.
Oooh and we should be able to "install" them using a nuget package :-).