Personally I found the idea that Cap never kills pretty silly.
He's a soldier that has been shown blowing up bunkers and shooting planes out of the sky in his earliest potrayals. He was a soldier in war.
I can buy an aversion to lethal force when it's avoidable. But he'll kill. We've seen that aspect of him from his earliest potrayal. It's not only more logical but more consistant with the characters orign to have him use lethal force if necessary. The notion of a war time solider that absolutely refuses to take human life is pretty silly if you think about it.
It's fine to have Spider-Man or Superman to have "no killing" rules, but honestly it never made sense to make Captain America that character.