I'm working on a character for a new high-level campaign. I've decided to keep the concept simple, and go with a god like Ilmater (Forgotten Realms) or Mishakal (Dragonlance). Both are pure healers, with the idea that you end suffering wherever you go and heal everyone, no matter who they are. In order to balance that with the fact that D&D clerics are actually moderately decent melee fighters, I was considering getting a weapon with the merciful enchantment on it. My dilemna comes from this being an upper level campaign. The weapon will be useless against almost everything we meet unless I put the money into it to make it a great weapon, and I don't want to do that. Which leads me to my question.
As far as I know, there isn't a cleric spell that allows you to temporarily enchant a weapon so that it does only non-lethal damage. So I'm consider asking my GM permission to alter the Greater Magic Weapon spell a little so that instead of giving a non-magical weapon a +5 bonus (at 20th level), I could give it a +4 bonus and the merciful ability.
Now, I can see how using this concept could get out of hand - use it to give your weapon the cold ability when you are fighting fire elementals, for example. But because of my character concept, I really think it would make sense for my character to be able to make her weapon merciful if she gets in a pinch and has to fight. Her domains are even the old fashioned good and healing. So, what do you guys think? Would this completely unbalance the spell? Should I suggest a variation ("Merciful Magic Weapon") that is one level higher than Greater Magic Weapon? Suggestions? Ideas?
Edit: I'm thinking of using the motto 'laughter is the best medicine' to model my cleric's personality around, making her easy going and with a good sense of humor, but not a clown. Kind of like a young nurse who knows how to cheer children up. Any suggestions about what skills might best compliment that? I'm thinking diplomacy.