With just a bit of time today I will offer some thoughts on this.
First, I doubt I would rarely design a course from the concept of putting it right on the edge of being too difficult. And this from a guy who currently has two courses that top their states in course rating! In truth, statistically (i.e. 95%+ golfers with 20 handicaps) there is little need for many courses to go over the edge on difficulty.
And I don't think the "precipe" is too hard to determine. While most are against this kind of analysis in favor of a more organic, flowing design, the truth is that with the Slope system, PGA Tour Stats, etc. its not hard to determine what size target area, what percentage of different type of hazards, what slope/speed of green will put an individual hole over the top for difficulty under average conditions for a given area.
Yes, the PGA tour stats for TPC Jacksonville or any course might have to exclude the worst weather conditions and perhaps the best to be useful. But, the USGA course and slope ratings were developed in the field, measuring selected courses in different areas over time (and thus different conditions) to figure out what type design made for difficulty.
And frankly, for the organic crowd, most gca's sort of intuitively know when this line is crossed, even when they do it anyway!
I believe its quite possible to design most holes with some flexibility in difficulty mostly related to the Sunday Pin location. I played one of my courses yesterday and on the 11th hole, which I had built on the Dustpan concept of Fox Chapel's 10th (?) hole, the pin was back up in the "panhandle" and thus very difficult, which was noticed by Lou Duran. But, a pin position in the front of the green, built to collect shots, would have made that hole much easier.
If most of the greens are of that nature, a coruse can be set up to the precipe or set up for ladies day. Of course, set up can relate to rough, narrowing fw, and a lot of other things to make it hard.
I consciously limit the number of holes with a penal approach where only a perfect shot would do, as would most of the golden age guys who favored the option of playing for the pin rather than a perfect shot. IMHO, there should be a minimum of one green of that type, for change of pace, preferably two. Any more than that, makes the course over the edge of playability, and many would argue that this is two too many. I design narrow fw, wild greens, deep bunkers, etc. etc. etc. on about the same concept - a few are okay, but not too many.
The real question is, IMHO, how many of these forced difficulty features can one course stand before it gets over the edge. That can vary with the role of the course, the site (with my Quarry as a destination resort on a site lending itself to tough sand hazards an example of when to go over the top) and the wind on that site.
In the end, only a few think a hard just to be hard course is also a great course, don't they? If we say that about older RTJ course, for example, I wonder why designers of any new course tend to think theirs will be different.