You're mixing arguments from different people and throwing them together as if one person said it. IMO it diminishes your arguments since neither KrayZ33 or I mentioned Death Note but you're throwing it around as if we made that statement.
What you're basically saying in your second paragraph is "Why should we accept any genius type/OP character that doesn't have any kind of believable reason for it (that I can accept)?". The short answer is: Because it's fiction. Sure plot armor exists and is applied to Inaho but I sure didn't start watching Aldnoah.Zero because I wanted realistic action/setting/characters/plot. I honestly have no idea what you expected a mecha show were mechs have super powers to be like.
Does it matter that the basic idea wasn't special? Would you accept it more easily if it was some sort of absurdly elaborate plan that no one would have ever thought of?
I should have you summarize all my posts, the point would probably get across way easier that way.