Wow, that is pretty awesome. Is there anyway to get Intellisense into the command window for CSI? I, all of a sudden, realized that I don't remember properties of the objects without it.
Theoretically you could implement a completion system for the terminal but we reused the WPF editor layers for the completion system rather than building a new one from scratch, so it isn't available in the terminal.
Also, all that is open source at https://github.com/dotnet/roslyn and the scripting core can be rehosted as an API.