I was talking to Hasbro Design Manager, John Warden at Comic-con on Preview night, and we had a great, long talk. One of the things he asked me to pass on to the Joe Community is that he has been watching the reaction to the color of the current HISS tank and wanted to assure us all that future releases of that mold will come in classic BLACK(and I would guess other colors as well). He was eager to get the word out, so spread it far and wide!
He also clarified the dual purpose of the hidden compartment in the back. It could be used as a gunner station, or as a place to restrain Joes captured on the field of battle.
He further described that the windowless canopy was to address the fact that glass-cockpit tanks aren't all that tough (a frequently raised point about the fragility of an original HISS tank on a real battlefield). He described that idea is that the inside of the canopy is a full video wall with a targeting HUD fed via external cameras.
He also is rightfully proud of his new "Shadow Tracker
" design. Hit the link for more info on that picture, and don't forget to have a look at the SDCC 2010 Gallery