Without humans, I don't think the TF prequels would appeal to a general audience really. Besides, a lot of the prequel stories have already been told in comic books. Suits me fine.

I'd personally love to see IDW attempt a prequel for Beast Wars though... answer questions like:
+ Just how did Rodimus and the Wreckers win the Autobot-Decepticon War?
+ How events led the signing of the Pax Cybertronia? Was it really a benevolent peace treaty or was it the Autobots enacting Gunboat Diplomacy to exert unchallenged power and in the process screw over the Decepticons (just like the Pax Britannica did on Earth during the British Empire). It would certainly explain the extreme political imbalance between Maximals and Predacons, and why the Beast Wars broke out at all.
+ The origins of Protoform X and Depth Charge's fall from grace.
etc.

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P.S.: Also, I don't think Hasbro would be keen on supporting such a project as a movie or cartoon unless they were intended to design a toy line for it. Remember Movie Protoform Optimus Prime and Starscream (and how they peg warmed)? Imagine an entire line of Transformers that looked like that! Well okay, you wouldn't need to change Megatron... but every Transformer would have these very alien looking forms that transformed into strange alien-looking vehicles; not sure if they'd sell.