As far as an anti-sharing policy, I mentioned a clad iron anti-sharing theft solution months ago.
My bad then. It sounded like you had an anti-sharing theft solution.
Let me give a staff perspective on theft. Things that get stolen include characters, items, gold, and clans.
Of these, stolen clans are the easiest to spot and deal with since the clan sale is both not immediate and requires staff intervention.
Stolen characters are the next easiest. Characters are relatively easy to track as they move from account to account since all transfers and name changes are logged. Beyond that, players can often identify characters that are stolen even if they have been name changed from public data like their level, stats, and kill list. Since we now have staff on almost all of the time who can lock accounts, this turns out to be easy to stop once a problem is reported. Dividing up an account of characters fairly is also no easy matter and often takes more time than finding out what happened to the characters involved in the theft.
Items and gold are almost impossible to track down if a thief is motivated. They are the easiest things to hide, easiest to re-sell, easiest to distribute quickly to a variety of sources. Since my cobalt and your cobalt look the same, finding out what happened to all but unique items is very difficult.
Personally, I'd love to see your solution implemented. As a player, I haven't sold a character in the five years since I started playing and probably never will. I think people should spend more time training and less time just buying what they want/need. However, most players really enjoy the ability to trade characters so that they can either improve what they already have or try something new.
It seems to me that your solution adds significant complexity to one of the aspects of the game that many players really like without providing any real safeguards.