And for the witnesses, I would put the vote every six months. We need to speed things up or get the members more active.
Currently, if you don't change votes, your vote will expire in 6 months... So, that's already implemented...
What you said for proposals is similar to that... The vote could expire in 3 months, and then the voter should "reconsider" to vote again or not...
All this, without the incentives, would be impossible to do as it requires even more time than now... But, I like the idea... :)