I'd love to see that sort of option! Allow people to keep their favorite sets as they attain new levels... as long as its costly enough that they put in three times the effort getting a new piece requires. I would have it cost less raw materials... but also require tempers! (which at high quality ratings, are a good deal harder to get then just raw materials you can just pick up in any of the right areas) Perhaps even style materials, though that would make non-leranable styles like akaviri, yokudan or the undaunted dungeon helmets/shouderpieces unimprovable, and I would expect a lot of people would want to improve especially those due to difficulty of getting them...

Improving jewelry will have to wait until we get jeweler as crafting skill, which may or may not happen... I hope it may, someday, though they really need more for them to craft then just amulets and rings to make implementation worthwhile... not like that is too big a deal of course, there's always stuff they could add for just that reason, from crowns/circlets/facemasks, to an alternate destruction / restoration magic weapon...