If on the climb-out your engine quits, you would push the nose down and maintain best glide, but aside from that would you attempt a restart? It's fairly quick to select a landing site in your field of view and then move on to a memorised restart drill, and then make a radio call, and then go through a memorised shut down drill before concentrating on actually landing. If you are going to turnback and you make the decision before-hand, surely there isn't the time to do anything other than turnback immediately and forget everything else. If the engine was actually on fire, you'd want to complete the shut down checklist, even if turning back wouldn't you? What about feathering the prop? I wonder how much altitude would be lost while undertaking these tasks.
It would be great if a standard procedure could be developed to give pilots a rough idea on the chances of a successful turnback, and I agree "success" bands would be a very good way to relay that information.