I'm not sure if this is the correct place to make this suggestion, so many apologies if I have made the wrong decision.
I remember, a few years ago now, there was a chess site, whose name I forget though chessworld.com or chessworld.net comes to mind. This site had a feature which I found very entertaining.
Every day, sometimes twice a day, a master game from the past was re-played on the website..Each contestant had to guess which move was played next. The contestant would then keep guessing the next move until checkmate or a resignation had been reached. The scoring was reasonably simple. A right answer would score 25 points anything else would score 0. I believe that there was a minute for a guess to be registered by a contestant.
The winner, naturally, was the contestant with the highest score and, if I remember, free month's memberships were given out as prizes for the top three. I would not expect any commercial site to implement the free months incentive.
I wondered if anyone has come across a feature like this and whether there is any appetite for something like this to be implemented here.