The copies would need to be encrypted kind of like freenet style, and it decrypts as you log in.. the passes could be hashes that check in the blockchain so it's like keeping your private keys from bitcoin safe... just throwing in some ideas.
It could probably be done but im not a good enough coder to actually get it working. I would wait until we have sidechains, I don't really see people throwing in electricity for a PoW that only servers this forum, we need to take advantage of the BTC blockchain hashrate.
Too complicated so for now we'll have to deal with the ddosers the oldschool way.
I could probably do quite a bit of the signatures stuff. The transmission would be what I struggle with though but that could already be sampled from the regular core.
As for the proof of work, that would be done whn you post, each post is a block and y'all get the score (or it could even be each topic is a block, you download the block, sign your new block, verify the entire block after checking the signatures of all the transactions/posts inside of that block/thread)...