A new model for publications where papers evolve over time?
Versioning of articles is supported by arXiv for exactly the reasons that you mention.  Each version of the article remains accessible and has a unique identifier, so when citing an arXiv document, it is best to use the version identifier.  A person following the link, however, can see that there have been updates since the referenced version, and use the updated information.

I'm not sure if any other publication venue offers this, though. I think that bioRxiv does, but it doesn't make it clear the way that arXiv does, and talks about replacing an article with a link to the final published version.  It's pretty new, though, and its policies may well be in flux.