Would you be more interested in playing a Transformers game where you control Optimus, Bumblebee, etc, or one where you make up your own Transformer and play along with Optimus, Bumblebee, etc? Let's assume this game doesn't take place in any specific universe (Armada, Animated and so on) so you don't have to follow an ongoing storyline.
I think both would be fun. In a "build your own" type game, you have more oppourtunity for multi-player games, but with the ability to select the main core characters, you may have the players bickering over who gets to be Optimus, Grimlock, Insert favorite character here, etc. What I think would be really neat would be a game where you start as a human, either a civillian or EDC soldier. You team up with the Transformers and gain the ability to control robot characters through a Grand Theft Auto type control mode.When the bot transforms, you can then switch between human and bot characters, for the humans can enter spaces the bots cannot. The humans could also carry small devices such as cell phones, mp3 players, weapons, etc. The devices transform into robotic familiars, able to atack and defend the same way animals can in fantasy rpg games.
I think you should make the game open for new Modifications like players and Weapons so that the whole game isnt based solely around some characters. Besides that the concept is great!
I'm making a game like that for my computer programming class. http://www.tfw2005.com/boards/showthread.php?t=167354