I will agree with you Escobar that perhaps it should be just +skill alteration since keeping track of the numerous multitudes of differing other stats would be daunting and arduous , I just wanted to somewhat steer away from the current trend of +skills currently being the only goals for end-game suits of players.
Also I agree the price should be high, but I'd be wary of "rich getting richer" by allowing players with only super-high amounts of donation or EDs to obtain these possible changes to their jewelry. Not everyone can afford a 500ED or more item, but 200-300ED is, I think, within the ability for any intelligent player to obtain through trades of services or selling in game items. High prices will only allow for the inflation of the Gold to ED purchases between players. EDs are only worth what players are willing to pay for them, and currently, the Gold to ED amount is significantly high (but that's opinion, not fact based)...
Lastly, a TOTALLY think Meta might be onto something with the whole "in game quest" completion option to open this ability for players. I fought very hard for a level-able spell book and suggested something quite similar about having to turn in 1 of each magi quest reward (each magi quest reward is random so obtaining all these items would be difficult to "turn in") or 10 of one specific magi quest item (10 magi staffs)... I forget the exact numbers suggested but it was somewhat reasonable and I though would allow to help reinvigorate the magi quests. Perhaps to obtain a +skill change from a GM would require a player to obtain one item from the magi quest, one item from the pirate quest, one item from another quest...this would reinvigorate these quest....
I personally thought a level-able spell book to distinguish mages from dexers was a great idea but i'm not sure how closely it was evaluated, so I highly doubt something like this would be implemented.
Thank you both Escobar and Meta for responding! It's an exciting idea I think... end-game content is hard to find in mmorpgs but just trying to add ideas to a great server that has many other customization and isn't closed to the suggestions of others for ideas to help out!