Most players I think can agree the guardian is just a very bad overall gun. Very few people enjoy using it, yet it's still insanely powerful with it's 1 taps to the head.
But because this gun is so difficult to use well, I think it should be changed to an automatic sniper rifle similar to the scar from cs:go. It would be the stage between the marshal and the op at 4000 credits and be a guardian but with a sniper scope dealing less damage.
150 - head
50 - body
35 - legs
Damage remains the same despite distance, damage lowered by obstacles (wallbanging)
10 bullets per magazine, 4 magazines so 40 bullets total.
Same fire rate and recoil as the guardian
Like the operator and some guns, the bullets would have piercing and allow multi kills.