Hey LilxPaprika,
While your idea is pretty interesting, there are some immediate problems that could be seen with an implementation of this system.
Firstly, the new voting system could be seen as very confusing. The upvote system is seen to many as an indicator to what is a current / popular thread. While this is a very simple format, it's extremely effective and introducing a secondary system could very possibly complicate things. Secondly, many people go to a specific thread to see the original poster's opinion, and then the discussion follows on from that. Upvoting the first post of a thread may not be seen to agreeing with an OP all the time. There are constant discussions on the Boards, where with many users upvoting the topic of the discussion, even if they disagree with the opinion offered by an OP. Thirdly, the vote system already has a flaw in that it may be suspect to vote manipulation. If your idea was introduced, it'd be suspect to vote manipulation far more frequently than concurrent discussions that get flagged with vote spamming. In theory, it'd be far easier to launch a troll thread, and have a dedicated personal army to launch it into the front page of the Boards, or at the very least shove it to the top of whatever topic section it would end up being posted in.
The voting system is simple in design. While I agree that sometimes things can err a little bit in regards to thread visibility / popularity, sometimes simple is often the best, and a 1-vote system, while not perfect, certainly has beneficial effects. Introducing a secondary one could complicate the simplicity of the one-vote sysetm.
-- Furor Nexis