Making an autoaim for Tribes that works for anything other than the laser rifle is very close to impossible because of the projectile based weaponry in tribes. In a game like CS with all instant hit weapons, you can just lock onto players and fire, hitting them every time. Oh yeah, at those jetpack things. In other FPS games, you're glued to the ground or whatever you're on and only moving in 2 axes(except when jumping, of course, but even then you know right where the person is going to be in .5 sec). In tribes, you're often moving in all 3 axes at once. An auto aiming plasma turret can hit you from close range, but the turret isn't moving at all. Most times, both you and your enemy are moving in all 3 axes, added on top of that the gun has to lead its target. And then that's not even correct, because you could already be starting to jet up, down, left, right, back or forward while the weapon is shot, so by the time the projectile gets to you, you'll be gone.
Sure there's been auto aim's released that try to aim for you or show you closer to where to aim, but none is truly accurate. On top of ping issues, trigger delay, the projectile based weapons, and 3 axis movement, auto aim should be one of the cheats you worry about least.