Ive seen and participated in a few skill matchers, from fps to rts. The best skill system ive seen is Starcraft II's system.
A weighted assumption of skill based on dynamic factors like damage to kill ratio's. Modifiable hit percents. Inclusive of damage recieved.
A BROAD sense of skill boils to,..
Aiming
*placing shots where you want them, IE (ct/weapon vulnerability)
AND
Manuevering/Tactics
*Back armor damage, cockpit damage, 1's own damage taken, 1's own damage spread
IE (shoot em in the back, loose all your other armor before your ct)
The Elo levels should also be weighted somthing like 6 tiers in percents.
IE 5,15,50,15,10,5 ranked in percentage lowest to highest.
I also think there should be a *Casual* mode where stats aren't tracked, for those times you wanna bring a 9 flamer HB into an assualt

PS: The casual bit shouldent be too hard from a theoretical standpoint. I mean copy paste standard game code, comment out the "//save to server". The hard part should be slapping a new button on the main menu :/.