On the other hand, I'd like to know how many people constitutes your new experience as an indipedent consultant? Infact, as others noted in the comments here, what you suggest is perfect especially for an in-house SEO situation or in for an Web Marketing Agency with at least 5/8 people working in. Even if all you say is correct and hopefully what everybodies should do, I honestly find quite difficult to dedicate all the amount of time and dedication in order to check all the steps described in your post. Or, at least, I cannot imagine myself doing it for all the clients.
Lastly, it's important to remember that paralysis by over-thinking is a real issue some struggle with. There's no pill for it (yet). Predicting perfection is a fool's errand. Get as close as you can within a reasonable timeframe, and prepare for future iteration. If you're traveling through your plan and determine a soft spot at any time, simply pivot. It's many hours of upfront work to get your strategy built, but it's not too hard to tweak as you go.