Megatron originally supposed to be a triple-changer?
Found this on Google images:
http://www.dk.co.uk/static/spreads/all/4/3/9781405341134L_008.jpg
It's his Cybertronian Jet mode from the first film, and his Cybertronian Tank mode from RotF.
Seems pretty cool. It also says "vehicle mode", so I'm thinking it might be a small reference to Beast Wars. When the quantum surge came, it altered their bodies and gave them a third "vehicle mode", in addition to their beast and robot mode.