Without commenting on future plans (that’s for Keith to decide), it seems to me that a number of these are not really related to Scrivener. For example reading a proof isn’t something you need a writing studio to do. All of those features and views and sorting mechanisms and index cards and so on. You’re asking a lot of your readers to navigate around in your work within this environment, when a simple PDF would have done just as well (nevermind that gives them the choice to read it however they like—maybe that’s with a stack of papers in a cozy chair rather than sitting up at a workstation). So for this list, I’d suggest:
Owner: Scrivener project
Colleague: RTF/DOCX etc. They can use whatever word processor they are comfortable with to add comments to the text. When they are done, you drop this into the Binder and review their notes (which will be imported as inline annotations or inspector comments). Since you’re just reviewing the comments (something Scrivener is inherently good at), it doesn’t matter if they mess with the text really. You’re just using that is a reference to work on your master copy in the Draft.
Reader: Simple, PDF output.
Editor: in this case, I would say that if your editor is amenable to concept, sharing the .scriv project will be beneficial for most people. Either hot-potato, or some kind of shared sync folder works well. With the latter you want to make sure everyone is on the same page regarding sync health.