The sink idea seems too artificial. Items should naturally get in and out of the game as people play it, the economy shouldn't require people to throw items down a well because the staff team asks for it.
The idea has nothing to do with staff, it would be a feature. It's about as artificial as elemental whips being a whip sink.
Putting the whole suggestion in the simplest terms to make sure that I understand it correctly(feel free to correct me if I'm wrong at any step):
A wild well appears.Well: "Giveth me stuffeth, I shall giveth thee doubleth exp'rience."
Tulrak: "ok"
Tulrak gets some items.Tulrak tries to throw items into the well.Well: "Wellmast'r
Thom'r alloweth not this, for
Charr hath said nay junk"
Tulrak is confused.Tulrak: "ok"
Tulrak: "Which items can I dump into you then?"
Well: "I accepteth stout armeth'r yond has't a huge supplyeth"
Tulrak: "ok"
Tulrak throws good items into the well.Tulrak: "Where's my double experience?"
Well: "I giveth doubleth exp'rience at which hour oth'r people has't giveth me stuffeth as well"
Tulrak: "ok"
Tulrak: "But what if I'm not online at that time?"
Well: "Thou receiveth a valorous w'rd on a listeth of contribut'rs"
Tulrak: "well, Well, can I get my stuff back?"
Well: "Thanketh thee, cometh again"
If that is the plan then the problem is that the well doesn't have any way of getting information about which items need to be sinked from the game itself, so Wellmaster Thomy will have to manually adjust which items are accepted by the well. Which will mean that the Wellmaster will have to get the well to ask players to throw certain items into it, resulting in the well being run by the staff and I would not want an economy where the staff needs to pressure players to give up their items.
Not to mention that Tulrak wouldn't throw his items into the well the second time.