Yeah that would be cool. Being able to design and color each body part of the transformer, choose a vehicle mode, all that good stuff.
If I was a billionaire, I would make PS3/X-box game set during the events of the original G1 series. There would be say, 3 playable characters from both the Autobots and the Decepticons, with the option to create your own character as described above, as well as a vast supporting cast. I personally would make it a sandbox-style game where you could free roam and explore and accept missions from your superiors, like Megatron, Starscream, or Optimus Prime. Also, in my own perfect world, the origial voice actors for all characters would return for the job.