Add VBA projects
I think the ability to create a VBA project for Word, Excel, Access (the only difference would be the IntelliSense support for the predefined "ActiveDocument", "CurrentDb", etc) would be neat. Of course we would then need to copy and paste the code into the VBA IDE but, for me, it would still be less painful then writing the whole damn thing in the default IDE.
With Rubberduck giving the VBA IDE features like unit testing, git source control, code inspections, refactorings (rename, extract method, etc.), a code explorer that drills down to members and fields, lets you organize modules into virtual folders, navigate "todo" comments and any declaration, locate identifier references and interface implementations, automatically indent your code, and exposes a reflection API so you can write VBA code that iterates its own types and members without having to trust programmatic access to the VBE object model.... how much of a pain is it to work in the VBE?