From what I have read, at the 2004 Joe Convention, one of the Hasbro designers said that the Nullifiers were planned to be released as the Cobra-La drivers of the Insecticycle. The symbols on the chest were meant to be Cobra-La-ese. Since the idea of Cobra-La was scrapped, the Nullifer was reassigned to the Iron Grenadiers.

This idea intrigued me, so with a more appropriate Cobra-La paint scheme, the Nullifier has been re-reassigned back to his right affiliation.