But it got me thinking...
I could honestly have seen this story originally proposed as a story arc for the Transformers comic in the Marvel Universe. Let's see... aside form our usual antagonists in the form of the Decepticons, we have a new, massive antagonist with immense power that consumes entire planets to provide the energy it needs to survive.
Does that sound familiar to anybody? Galactus has immense cosmic powers that we know he can bestow upon other beings, so the small matter of rearranging a few robots into more powerful configurations (IE, Galvatron, and his new Decepticons) would be a small matter.
I'll grant, there aren't any of the other staples of a Marvel tie-in, but I think that the similarities between Unicron and Galactus are too powerful to just ignore. Especially considering the fact that we're never given an explanation of why the Autobots Matrix of Leadership was able to defeat Unicron.
And in all honesty, wouldn't it be cool to see the Autobots and Decepticons unite to confront the threat of Galactus? Heck, you could even have thrown some Spaceknights in there too. Who knows... maybe Cybertron will show up somewhere in Annihilation: Conquest.