Cow's weren't boring, just finding a maker was. endless runs where the cow king was killed each game. I reckon if they do nothing else, at least make it so the king doesn't make the level unmakable when he is killed.
Let's face it, farming the king wont get the best items in the game and is not any faster then farming mephisto, so I dont see the problem. Furthermore, Players that do mf alot probably have a maker make the portal and then come back with the mf'r to kill the king anyway.
Having the cow level remakable whether the king is killed or not might jsut start up a few cow runs in hell for that added change from baal runs.