Not bad
An interesting take on a classic. It reminds more of Halo, though, than anything else (the fact that it takes forever to kill someone, but it only takes someone else two shots to both steal your kill, and take you out...)
There should be mobile cover/obstacles that roam the playing field, such as (what else) asteroids. Temporary power ups and multiple game modes (CTF, King of the Hill, etc.) can also keep this game fresh.
Hope you take my ideas into consideration.