Hello Brian,
Though you posed this question awhile back I believe there could have better responses from within <a href=“http://devnet.jetbrains.com/community/wi?view=discussions” target="_blank”>Webstorm or <a href=“https://developer.appcelerator.com/question/16921/titanium-forum” target="_blank”>Titanium community forums.
Believe you are able to use any IDE and use Studio to build though unsure about the autocompletion part but there should be libraries for that.