Even if somebody makes hundreds of edits in good faith, there will still be a good deal of inaccuracy in some of the edits. A rep system built on trusted edits does not mean the quality will be any better. Whatsmore, determined vandals could start trying to access accounts through phishing.

I'd say that downloading and viewing paedophilic pictures is rather different to actually abusing a child. It would take a certain leap to jump from images on a screen to real life. Perhaps an "internet ban" (leaving aside any potential difficulties with enforcement) will prevent the individual concerned from developing a "taste" for children, and eventually finding that simply viewing is not enough.