I was thinking this over during the night, someone brought up the ball and chain knight, so I reviewed Transformers: Devastation, and some other canon Transformers material. This could work, but would require some work.
You grab the Triforce, it would warp you to another screen, triggering his intro.
Basically, the fight would work something like this:
Megatron woold open in the beginning laughing at you, then transform into his tank form from Devastation. He would then be blasting, forming a ball and chain type shield (in this form he would be invulnerable of course, if you try to attack him, you take a crapton of damage). You'd wait for him to get to the side of the room, then he'd transform. He's load up for his signature arm cannon blast from Generation 1, then blast it hard across the screen. After he misses, you could damage him before he transforms and starts the tank segment over again.
After taking enough damage, he'll go into desperation mode, and instead of straight line shot, he'll fire a three-way shot. At that point, if you survive, hit him three more times, he dies, and his ending line triggers. After that the Triforce drops from the top. You grab it, Level 7 Triforce.
Video detailing the Devastation Battle:
(sorry, my no death goes too quickly to show his attributes, I apologize. Had to use someone else's)