These are all solid ideas, I think #1 identity verification is the best idea and I've already expressed frustration to my friends that people with a multitude of accounts would only open the extra accounts if they feel there is an advantage to doing so.
In my view the presence of people with an order of magnitude more accounts than anyone else is fundamentally unhealthy for the platform, I've already personally experienced being attacked by a down vote bot.
Maybe they will implment it soon.