I'm sorry, are you suggesting they were planning to kill The Vile Excrement during the writing process, only to change dead to mostly dead? My answer would be, I don't think they would have cut off his head unless they meant to, it was intended to be like a severed limb or a severed thumb to a human, a painful experience, a permanent scar, but not an execution proper, the Yazuka only wishes to punish and reprove failure. If you look at the Romans, a warrior society like the Deathwok Clan, beheading was considered an honorable death, when they hated you, they had various means of making your death an entertaining one, not to mention sacrifice. If your question is, was Lorne a valuable member in season 3 & 4, yes, I believe his continued existence outweighed any value his death might have had, like establishing the brutality of a demon world.