The idea sounds pretty appealing to me. The chances of fail/success should mirror that of the original refiner, and the catalyst at a decent drop rate; not too high so that it takes a few seconds to get, but enough so that even a small economy can be made for the catalysts. As for stats I'm not too sure, but why not bring in some custom cards requiring a refine rate? Could be an improved version of a card we already have (e.g Improved Tao Gunka +40% Hp Req. refine 9~10). Overpowering shouldn't be a problem, since making a high refined item would be a feat, and the player would think twice before possibly throwing a 100 coupon farmor down the drain. And lastly, this could be the "expansion" that some of our players are wishing for.
edit: I like this idea since it would be (imo) an update that would distinguish us from other servers, not just the new item updates we've been getting, that certainly does not distinguish us from other servers. it could potentially have the magnitude that the elite quest had, when it came out.
btw i write 2 long.. sigh.. read tho pls!