default01 I think you just open the whole controversy here, since it is not a real challenge to the developers. In my opinion the resign option is just fine the way it is. You only get 7 points, but you kick one player out of the game. If that player finishes last, anyway, then why declare war on him? If it is the leader, this exactly prevents the kingmaking you're talking about. If your strategy depends on winning that one war at the end, you're playing it just as bad as the opera/culture player. After declaring war you have to take into account that the other player resigns. This gives an incentive to declare war on the leader (because he might think he still has a chance to win after the war) rather than the one who loses, anyway.
On higher levels I have seen this very rarely. Most good players don't get into that situation so easily. They build military and culture alike and won't be fooled into building tons of urban buildings without protection. To me this shows that the mechanism works. If it was broken, you would notice it on that level.