The fully integrated experience you mention would do a lot for the Julia community in terms of gaining users tied to the GUI elements of MATLAB and VS for other languages. Integrated debugging and inspection in particular is a long-requested feature that has yet to see much attention.

Integrating with Pkg as Julia Studio does would be another important feature, as well as providing some sort of integrated plotting/graphics widget (a backend canvas along with plot navigation and image export, ideally supporting more than one of Julia's plotting backends).

I would certainly contribute to an alpha- or beta-testing effort :)