plus or minus, huh? that's pretty cool. i could see this giving +/- 2 instead of 1

Is this supposed to allow +1/-1? -1/+1? Or is it just "Target creature has an increased margin of error, and when it hits stuff you can be fairly sure they're dead, but not certain" and is then mostly usable in quantum magic?

It grants +1/+1, +1/-1, -1/+1, or -1/-1. I like you idea, though.

Amusingly, +1/+1 is white (or green or black), -1/-1 is black, +1/-1 is black (or red), but -1/+1 is blue (or green). Defensive Stance, Pemmin's Aura.