I would've loved it if they brought up a different version of Transformers for a Mecha, like the Beast Kingdom (I think that's what it's called) version. Basically all of the characters you know and love get mutated and turn into animals instead of vehicles. Optimus Prime becomes Optimus Primal and I don't think Megatron got a name change, I think he had some sort of dragon form though.
Close, those weren't actually Optimus and Megatron, they were future TransFormers who had similar (in Megs' case, ripped off) names. They were advanced enough to take organic forms when they reached the past. He did get a Dragon at the end, it was weird...but cool.
I think an OHKO kinda defeats its defense purpose, most things that want to be OHKO'd, for me at least, require just sitting there and spamming it until it works, regular enemies don't really need it, just impossibles.