Yes, I have proposed an idea like this some time time ago, and it is waiting on this forum to be picked up:
I see the forum as a first-stage archive, a body of raw information that is waiting to be processed. In this regard old threads are not forgotten posts far down the topic list, but rather inspirations and TODO’s.
You can filter on the ‘idea’ and ‘collaborate’ tags to find more of them, and of course, there are many, many posts that contain the fruits of ideas that we can pick up on as soon as there is enough interest. If there is interest, but no follow-up (like with the book club idea) then the idea remains idle in the archive.
PS. I should make this part of the FAQ, i.e. explaining how projects can be initiated on people’s own initiative.