I liked your thinking, but I’ve just checked and Change Timestamp is only in the topic wrench, not the post wrench, so I don’t think it would be an easy option.
The Make Wiki option is a default Trust Level 3 perk (though this can be adjusted in the min trust to allow self wiki admin setting), which allows the post to become editable by anybody TL1 or higher (also adjustable). Wikis don’t have to be the OP, but they do tend to get lost if they’re not. 
Though you can search for them using the in:wiki search filter.
With a wiki as an OP, it allows it to be updated with new information/edits by the community (depending on the TL settings you choose), and the previous versions can be viewed through the edit history (in top right corner).
I’m not sure that fits with what you’re after, but I still can’t quite fully see what your end result would look like. Could you give me a rough example of the first few posts in such a topic so I can have a go at replicating it on my test site?