- Accounts from hero to legendary rank should not be allowed to change email in order not to be able to sell such accounts.
Ridiculous, have you considered email provider could shut down it's service?
- Accounts not active for a year should be temporarily disabled and can only be activated after passing some verification that seems suitable by the administrators.
Not ideal option if we want more people participate in this forum. Additionally, it'd waste moderator/admin time.
- Change of account email should have limit to avoid multiple change of ownership within a short time.
It'll annoy few user and i doubt it's effective option. The seller could sell both Bitcointalk account and email address at same time, so buyer only need to change Bitcointalk and email password.