Gene,
That's a great, great question.
Firstly, to be fair, though spectacular, the rocky site had plenty of negatives include poor soil, little in the way of natural undulations (more broad slopes than anything else), and severe weather which makes holes along the cliffs an agronomic nightmare.
In thinking about it, the routing does not appear to be the culprit. The architect gets the player to the cliffs in well spaced intervals throughout the round on holes 2-4, 7, 12(!), 15-18. Of course, are they necessarily the best holes that the site had to offer? Perhaps/perhaps not - I don't know what land wasn't used but at least 9 of the 18 holes are memorably situated. Plus, the architect's use of the natural topography on holes 2, 4, 12, 15, and 17 is fine indeed.
Thus, the routing appears good enough in my book. However, beyond that crucial first hurdle, not much else works.
The clumsy use of mounding stick out on the broad slopes and are clearly unnatural and man-made, like the row of mounds down the length of the 10th hole
.
The greens and the slopes around the greens don't tie together well. The polar opposite is the Plantation Course at Kapalua where the golfer can use the surrounding land to help work the ball toward many of the hole locations. C&C created several front to back greens by allowing the greens to follow the broad slope of the land - why the architect didn't do the same at Old Head is a mystery.
Instead, the golfer is given one bland green complex after another as a target. The direct result is that the ground game is patently uninteresting here - which makes NO SENSE, given its windy location.
Plus in terms of strategy off the tee, I enjoy trying to hit the right shape shot on 2, 4, 12 (though they are all a similar draw) and I like the central hazard in the 14th fairway and trying to reach the 15th in one blow, but otherwise, do any of the other holes hold much strategic interest off the tee? I vote no.
Finally, while I appreciate all the views off the rock, the views on the rock are dullish, IMO. The bunkering is basic and there was no texture from the use of different grasses.
In a windy environment, the architect should give the player plenty of width and room to play. The player's thought process in analyzing the day's options and the route that he elects should vary from day to day, but that can only be the case if the holes enjoy a certain scale to them and if the holes are designed with the ground game in mind.
This was not the case at Old Head.
Thus, to answer your question, I would keep the generally routing but start over from there. I would re-do virtually every green complex, save for a couple like 2 and 4. The new green complexes would be low to the ground and the design would revolve around the ground game. The obvious desired result would be to make the holes/course more natural and engaging to play.
Cheers,