Implement Visual Studio and Blend as UWP apps
Visual Studio and Blend should be implemented as UWP apps, especially now that UWP supports multiple instances and multiple windows for an app, even though that could, possibly, have not mattered.
Developers in general will not have full assurance in investing into UWP if Microsoft doesn't lead by example by implementing their core productivity apps in UWP (some Office apps have been implemented in UWP).
Essentially, this can create the opportunity of Visual Studio being on all sorts of device form factors due to the responsive design and adaptive design capabilities of the UWP platform. And it would not be necessary to build separate development toolings for each device form factor, e.g. for AR and VR devices.
The approach can still be like the current implementation of Visual Studio UI in WPF mixed with other technologies and logics under the hood. If the UWP platform is not mature enough for this, please necessary pending features should be implemented to enable this to happen.
I have also posted something similar for SQL Server Management Studio at https://feedback.azure.com/forums/908035-sql-server/suggestions/34239007-implement-sql-server-management-studio-as-a-uwp-ap