I think that the Internet Archive is doing just fine in terms of being used as a way to save important parts or contents on the Internet, there's probably someone out there that's already doing what you're trying to propose and I think that it would be a really awesome thing if there really is someone doing it and not just some threads on the forum but the whole forum itself and when it happens, it will feel like you're exploring the forum itself when you check out on the preserved forum in the future that this forum is really going to go away.