Why has nothing happened to this?
Probably because nobody has found the time or interest to work on it. That happens some times - there are not many people actively working on CHDK who have the skills and knowledge to do this and they get busy with other things.
The solution with the record button seems to be fine. Is there already a ticket for this issue?
CHDK does not have a ticket system, or a schedule, or even much of a plan going forward. It's just a small group of volunteers who work on things that seem important or interesting to themselves.
The solution used with the S100 looks fairly easy to implement. If you'd like to test it, I'll need your camera model & firmware version.