1:1 voting is a great idea that I've been supporting as well. In your example, voting 2 witnesses would give them both 50%, but just like with upvoting content, it would be pretty easy to upvote one witness more than another.

Powerdowns are another issue entirely. There's some talk of being charged a "burn fee" to powerdown early, so you'd get the money back faster but less of it.

Personally I think we should have voting every month to determine if the powerdown time goes up or down. I also like the burn feature.