As an old member with a new account, I never really much got into the gangs. However, I also recognized that gangs played a vital role in the board activity and took off right when I left. I know it may sound stupid, but my idea to keep gangs involved would be to take a two week long poll, asking any member that is on the forum to vote on if they would want gangs back.
If majority rules, rework the forums to include an archives section, where any old material can be accessed (including old gangs), and then completely reboot the gang program, starting from the ground up. That way, old members can get a fresh start, and new members don't feel left out of the gang program. Just my two cents.