It's been said before but they could have left the Toyman/Superman/Aquaman pack alone and reworked the Guy Gardner pack to include Dr. Destiny and Firefly instead of Batman and Martian Manhunter.
It would have made MORE sense to just keep the six 3-packs as is and simply design a seventh 3 pack for Firefly/Dr. Destiny/Volcana. Since they had to create totally new packaging for the Toyman/Dr. Destiny/Firefly pack anyways it wouldn't have cost too much more. The only reason I can think of for why they didn't do it is that perhaps they thought it was too much of a financial risk. And since the last three 3 packs aren't selling as well as the first two did they may have been right.