well yeah but i mean AT LEAST allow you to duel your friend somehow
If you only want it to duel your friend, would you be taking it seriously? There are better games for that.
Would you ever say "____ is over powered! Nerf it now!"? If so, that's why they shouldn't make it. Take that stuff elsewhere.
Or would you just be goofing around, not caring about the fact that it's balanced for single player? If so, then we're on the same boat. Welcome aboard. Don't get too close to the edge. There are sharks in the water.
I don't even like the idea of co-op, people would be giving great weapons to low rank people and just ruin the whole point of the game.
People already give themselves uber weapons and armor via the console (on PC at least).