Your suggestion to use "Bitcoin block" for selection the winners is seems to be the best approach to find those who get rewards.
That's not what I said. I suggest this only for the $50 voting prize winner.
I thought about it, but I got the idea that if I did so, then I could be accused of mistrust of the forum participants.
If you have an offer and are ready to pick a winner, post it, I will add these terms to the rules and give my $ 50 to the winner.