Not sure LinqPad is the right way to go.

What I would like to see is a dedicated REPL application (likely based on the scripting dialect of C#) with IntelliSense and support for NuGet packages (if you want to have those features in LinqPad, you have to pay).

Kind of similar to Xamarin Workbooks, but better, and without all the "it's for documentation and inspecting applications" cruft.