One underlying Zope change still pending, in this vein, is the ability for an object to be optionally exempted from packing. Integration with other network access modes. Eg, FTP and WebDav x browsing and editing of wiki pages. Zope ZWiki already provides for ftp access, though it's rudimentary, and it's not clear how to provide for greater discretion about metadata like alternate document types, permissions setting, and so forth. Email is another possibly very interesting access mode - at least for appending to wiki discussions.
Email is already clearly an important mode for delivery of notifications.
Roundup may provide lessons that make the email-based user interfaces obvious and manageable, in which case this approach could be a win. Provisions for structuring documents to organize discussion and commentary. There's a number of thrusts, here. Simplest application would be accepting changes only at the end - weblog style. Next simplest would be one that allows insertions anywhere, for comments next to subject lines.