I agree with most of this with the exception of 3 and 4.
It has been my experience that most people lose for one simple reason: Wrong Dog Syndrome. I think I can count the number of times on both hands I've known of them to lose due to being overworked. Most losses have been from one dog simply being better than the other. I would say I've seen more dogs not in the RIGHT shape, which leads to number 4.
Whether it be a defensive ear dog or a barnstorming killer, they're all going to need air/stamina. I've seen countless people work a barnstorming dog for strength and NOT work enough for the stamina end. Invariably, the strong dog doesn't have the endurance to carry the show longer when needed. Barnstorming dogs need to be worked twice as hard as most dogs simply for one reason: breakneck pace. If a man wants a dog to be able to go at a breakneck pace for any length of time, the dog has to be in the proper shape to sustain that, and if a man just centers on the dog's strength, he's going to invariably fail when he runs into something that's in better shape that he's not able to barnstorm into submission initially.
I personally think working a dog according to a style is setting the dog up for potential failure. If you're going to try and account for all possibilities, you have to account for running into a dog that possibly negates your style, or better yet, is BETTER at said style than your dog. If that is the case, and you've tried to work a dog according to it's style, it won't be in any proper shape to possibly change up and go into a different style for a sustained time if need be.
I can think of a certain Cottingham dog that had won a show or two that was really good as a defensive head animal. All I heard from the owner was how those dogs had such excellent air and stamina. He believed in conditioning for style also, and I posed a similar question to him. What happens if you run into a better head dog than you? Is your dog in the PROPER shape to go at it differently if need be? Invariably, his next time out, he DID run into a better dog, and the dog was bottom dog around 40 simply due to not being in the proper shape for a different change of pace. He was in shape to control the show, but he wasn't in the proper shape to play catch up and turn the tide.
How you work your dog, or why, is entirely up to you. I just feel if you work according to style, you're gonna be in more deep water than need be when you run into quality dogs and not quality men.