Make it so its not credits as a reward for destroying a gankers ship and you remove the exploit incentive.
Make it an Elite rank (Security Elite or something) and make the rank Zero itself for 3 months, if you EVER gain notoriety greater than 1.
Players could gain Sec Rank via escape actions, scanning actions and enforcement.
For those who destroy clean players ships etc, they could have an Inverse rank, It starts at Elite for everyone but goes down the more clean you kill. call it Clean License Rank. (or something)
And change the ranks names to be increasingly attractive names for the Ganker minded players. for example :- Notorious, Infamous, Despicable, Deplorable, etc etc.
Thinking about it a single rank system with everyone starting in the middle would be simpler to create. Up rank names for goodies, Down Rank names for baddies.