An important thing to evaluate on a proposal is the level of detail and specificity, or lack thereof.
A good proposal should be very specific about all aspects of the job including exactly what equipment will be installed, quality metrics, timeframes with guarantees etc.
The exact design, engineering and architecture should be well thought out and described including 3 dimensional drawings from multiple angles.
Things like wall and floor thickness, concrete psi, rebar size and spacing should be specified.
Elevations should be described exactly.
Quality metrics like “level” should be specified.
Ideally, the contractor should also provide statistics on how well they meet things like timeframes.
The contract should be specific about when a breach occurs sufficient for the customer to cancel and what remedies are available in the event of a breach.
For example, the contract should specify exactly when the project will be completed and if it is not completed by that time, the customer can cancel and get all of their money back plus penalties for being late.
The contract should specify what, if any, circumstances are acceptable reasons for a delay.
Don't forget about the

Unicorn Clause

, which has as much chance of getting into most construction contracts as just about everything else you listed! The problem is:
we scrape the bottom of the barrel in terms of finding warm bodies to do trades work
Matt nailed it. Kids don't dream about becoming tradesmen or contractors. The pool from which contractors are drawn is the uneducated labor force doing construction grunt work that eventually get tired of having a contractor for a boss. So they decide to become their
own boss. Their entire construction management education consists of learning what is the proper paint with which to slap their name on the side of their truck door. That's it. Once done, they're in business! They'll only be able to apply whatever business acumen rubbed off on them when they were working for someone else, who probably had the same amount of construction management savvy when
he got started!
At least in my experience, you're lucky to get any sort of contract at all. Most contractors will do a proposal, of sorts, and then have you sign it, and then consider
that the contract. Some will provide a separate contract, but it usually consists of clauses designed only to protect the contractor! They probably got it from some cheap lawyer, or bought it off a website. Compounding the problem is the average consumer's lack of knowledge about what a contract is supposed to include. Like the building of their pool, they trust the "professional" to provide the necessary paperwork. But as Matt points out, that level of construction management is just never learned by the average contractor. Even here, in CA, where one cannot obtain a contractor's license without first passing a test, most of which consists of how to write a contract, contractors just won't use that learnin' once they start booking jobs. It's crazy.
So I don't mean to slight your list, James, at all. It's a great list. I love Guinness' idea of posting it where it can be found. Because only through educating potential contractor shoppers can this awful aspect of the construction industry take a turn for the better.