The suggestion to have it have a chance to fail is kind of iffy. Nobody would want to have their Forsaken King Gears broken, it would be like donating for one then throwing it away if they failed. 90-100 coupons down the drain for Forsaken King Gears, and around 5-10(?) coupons down the drain for Elite Gears.
Also, are you talking about like an item used for refining (eg. orideconds, eluniums)? I wouldn't say it would be overpowered, it just depends on how many stats you're giving. Although, you are on to something. What if we have this item you're talking about, and make it so that if you use it, you'll get a 100% chance of working.
And sure, I think you're expanding on the idea. Having something on my gears does sound appealing as well, but we still have to think of the overall balance of the server.