not a bad idea. I think the idea centers more around discouraging large number balance then it does focusing on scoring. So, guys trying to fly for rank might have a more difficult time achieving their goal if they are spending large amounts of time flying in the safety of a horde. It also does reward those who fight outnumbered. Ya, you could climb to 10k, but when heavily outnumbered, you generally not going to furball your way out anyway...so the tactic for dealing with this stays the same, it just rewards those willing to do so. In terms of fairness to the player base, well maybe up for some debate...but then again, whats fair about a horde.
The only issue I see, is it may only target a selected portion of the community, those who care about score. Who knows if it would have a large enough impact or not. Either way it is an interesting thought.