Jipe, the player would not be hampered in any way.
Say a 10x10x10 cube is created (big, I know). The player who invoked bullet-time is allowed to aim, dodge and lean in real time (or something close to it, maybe 75%). Running, jumping and shooting are still slowed down.
Now say another player enters the cube. He is subject to the same restrictions as the player who invoked bullet-time, but is unable to perform special moves like leaning and dodging, and his aim is subject to the slow-motion as well. Any shots he fires will be in slow-motion, but will speed up upon crossing the cube's threshold.
Were another player to fire into the cube, his shots would slow down upon crossing the vectors that define the cube.
Note that bullet-time would not protect against splash damage (so the player who invoked it would not be 'invincible'). Also note that bullet-time would not work with the force powers, and that it would screw up sabre fighting.
Finally, some kind of limit would have to be placed on the bullet-time, to prevent players from running around for long periods of time with it on. Maybe it could recharge every time the player scored a kill, or perhaps it could charge on it's own, like mana.
That's my idea...
COUCHMAN IS BACK BABY