Part of the problem is that the existing (that is, as of 0.995) knockback method reduced the damage output of exploding weapons that dealt knockback, due to the fact that damage received was determined by where in the explosion they ended up, as opposed to where they were when the explosion started - meaning that if they were thrown out of the blast radius, they hardly took any damage. Big problem for Radius 1 weapons, as exploding weapons don't actually deal impact damage. Technically, this would have also affected shotguns, but with those at least the target is almost always ending up on a tile where they still take damage anyway.
