To solve the backlog of AD exchange without much fuss or confusion is actually a pretty easy method.
1) create a time window for AD Exchange - make it no longer than 5 days.
2) All backlog items are given a 5 day window
3) Communicate this by a massive in game email to all characters
4) Communicate this by social media
6) Backlog is removed after 5 days
7) Pray that the servers don't crash due to the backlog
To me this is a straight forward way to resolve the backlog issue.
What the devs did in mod 13 instead is upset players who invested time or real world money by buying additional character slots to gain additional AD. The change in mod 13 really did not hurt botters as many already manage more than one account.