Trailing is already possible via steemauto or similar services, I don't have plans to integrate something similar in the near future.

The downvote issue has been addressed though. Delegators can register to the website and suggest posts to downvote. The weight of the downvote depends on their delegation in relation to the other suggestions. The clou is that we always use our full power - and as not all delegators suggest posts all the time, the resulting downvote will be stronger than what one could achieve with his own stake alone.