And how are points determined? Why by a direct relationship to kills!
As has already been pointed out several times in this thread alone, no, points are determined by many actions *one of which* is kills. So, no, there is no "direct relationship" between kills and points: you could score lots of points without ever making a single kill, to take an extreme counterexample.
Then go read how rankings are done for any of the Unreal Tournament games, for World of Warcraft's honor system (which is far from perfect, since there's no dishonor), or numerous other games (including open source ones). It's not hard. Consider each death event a one-on-one tournament
So your solution to (your imagined problem that) points are only given for kills is to implement a system which only works for kills? The BF2 system rewards players for many actions besides kills; again, I don't see how this system could be integrated with chess-like rankings.
Who's the better player? One who kills 100 newbies in the space of 4 hours and dies 200 times, or one that kills 50 decent players in 2 hours and dies 5 times? Right now there's no scoring difference -- they both get the exact same number of points.
There is no way of knowing who the better player is in the situation you describe because -- in case this hasn't been said before -- rewards in BF2 AREN'T JUST BASED ON KILLS AND DEATHS. Go play Quake 3 if you want such a game.
It would be trivial to adjust the current system to reflect time played, such as using points-per-minute rather than just points. I, for one, am happy they didn't go that route.