Well, instead of restricting it instantly, firstly allow them to sell their assets, say, give them a month's time. Then, let every MA select two accounts they can keep. Give them two weeks for this, or include the one month time aswell and give them a total of 6 weeks to select two characters. After that, LOCK the un-selected characters, deny access to the owners. Give a month's time and let people apply for a third character. They'd need very good reasons to have a third character.
At the end of these 10 months, delete the non-selected characters, and then make 3rd characters a level 5 donators only special feature where level 5 donators can apply for a third character.