Ways to version cloud-based Help

The rush to the cloud very much includes product documentation and support, so I've been looking for cloud-based solutions that support multiple versions of the same product. Note that I say "cloud" and not "wiki": that's because I'm focusing here on where it gets authored, not on what users end up seeing. Honestly, most software shops don't want end users editing content, but they care very much about letting everyone inside the organization be able to just open a browser to contribute to the documentation.

Here are a few approaches that I've come across so far:

• Confluence: The true wiki of the bunch, I think they add page statuses that control publishing/visibility, which lets them do a real publishing workflow; if not, they have tags on content that accomplish it – that is, upcoming content only appears to internal folks, based on user permissions.
• Author-it Cloud: Based on my prior experience with Author-it, I think it likely still works like this: Each page (object) has multiple versions, and a pointer flags one of them as being the current published version – which lets you draft the upcoming release version and also revert. Pages also have status flags, so I can find all the pages marked "Approved" (or "ver-4.01") and bulk-set them to Published. Then I set up publishing of the outputs with the appropriate statuses.
• HelpConsole: Cheap, but workable: they make versioning possible by having the wiki be the authoring tool and supporting automated publishing out to the actual deliverables: Help site, Word, PDF. If Product v3 only updates once a month, then I only publish out the Product v3 help site content once a month. If I have content that goes into both v3 and v4, I publish out the shared content to both help sites as appropriate.
• MindTouch: The dreamy tool for social, cloud-based Help, for both end-user and developer documentation (the only tool I found that can generate and merge API reference content into the wiki non-destructively). I understood them as saying that you can export from a staging wiki into a production wiki from a command line, so versioning would be similar to HelpConsole. 
• HelpIQ: Affordable and, like MindTouch, integrates with Zendesk. It is designed for web apps that have "living" documentation, so it has no built-in versioning. I was told they were getting numerous requests for it, so they're looking at how to support that.

Hope that helps someone! What have I missed?