It would be nice to have the following for Asp.Net.

UI only project libraries that are compatible with WebForms and MVC, and which are statically typed. Then at build time compile a portion of the library to object oriented JavaScript.

Design time support for data binding to the above mentioned UI library.

For inspiration see JSIL (on GitHub) or even Google GWT.

We all know that web apps are the only true cross platform applications. If MS wants to rule in this space and the future, beating the competition is a must. Please take a serious look at what Visual Studio can do to be the defacto standard in this area.