As for the campaigns deadliness raising... it has already happened. As soon as I brought them back from the dead, one player says, "I will now always take the time to chop the head from each of my fallen foes..."
But believe me, if that starts to happen, it starts to happen both ways... no more of the bad guys letting unconscious foes off the hook because they are defeated.... this is my usual policy, and I always reasoned that if a PC goes to negatives, he is no longer a threat, the creature who defeated him would move to a 'live' target and play would move on.
Of course many more times than not, the PC would get a Cure spell mid-battle and would again be in the fray!
If they start chopping heads, so will I!