Re: Stunning the target without damaging it
Just FYI, something very similar to this has been dealt with in an official Hero System product before.
Where, I hear you ask? (Well, see, I really don't, since my hearing isn't megascaled. I'm just saying that.)
In 'Magic Items', a supplement for Fantasy Hero first edition, copyright 1987. (How pathetic is it that I know this, and still have the book?)
Specifically, the Power Mace of Keshgar had an effect of 1d6 + 1 killing blast, and then a linked (except in that book they didn't use the limitation 'linked') 1d6 of killing blast with the limitation "only for stunning". Frankly, I like that approach... it's clean and simple. Of course, buying it as a normal-damage (or stun-only... perhaps ego?) might make more sense.
In campaigns where the DM is willing to bend a little, you could also go for a stun drain where you move the recovery *up* the time table a couple notches (thus making it recover faster than normal, in exchange for a limitation. Should be pretty obvious how it would work.)
--Adam Lang