Slashdot tried this, without much success. All the -1 mods were treated pretty interchangeably (can you distinguish between "-1, Flamebait" and "-1, Troll"? Is your distinction going to be the same as the next modder? And much of the time they were really being used as "-1, I Disagree" anyway).
As were the +1 mods, for that matter, save "+1, Funny".