I like that fact that OP sat down and reasoned all these out to share with the forum. I also appreciate the fact that some of his ideas are applicable, even if it will be bogus to implement. But what I don't actually is the compelling reasons to run a decentralized forum. If this was necessary, Satoshi would have implemented it before now.
If securing the forum database is the problem, there are many other ways to do that.
I have developed and discussed a merit-based ranking system that's fraud-proof/fool-proof ... it can only rank up reputable moderators/members. Incase you are interested, let me know and I will share it here.
I will like to understand your theory of the merit system that will replace the human conscience with machine codes. I highly doubt there's a chance of a better merit system than what we have now.