Adam has identified what is the only possible alternative site in St. Andrews with a link to the coastline. It is narrow and sandwiched between the main road into town and the upper reaches of the estuary. It is also very close to the end of the runway at Leuchars. Not exactly a rivetting prospect. Kinkell Braes was the only rational choice for the development of a course of the scale and stature required. It is as close to the town as it is possible to get and offers a completely different perspective of the burgh to all the other courses. If the Links Trust didn't develop that site then I'm sure somebody else would have.
Perhaps the only other alternative would have been to cut up the Balgove and Strathtyrum (and maybe the far end of the Eden, plus a bit of new land) to make what would be a 5th course. However, this would leave the Links Trust devoid of any beginner/novice golfing provision, which I suspect the provision of is part of their statute.
I've no doubt that the Castle was styled to outkingsbarns Kingsbarns. Stylistically, it is clearly of the same genre, along with the two St. Andrews Bay courses. Who knows what a 'natural' course on that site should look like. There is no natural ground left anywhere near the town for reference. Agricultural land cannot be considered such.
A far as I'm aware, the decision on the allocation of the site was made long before the selection process, though DMK did lobby (succesfully) for some additional land to create Green 16 and Tee 17 (which we didn't have to work with when preparing the design competition). It isn't often in my experience that one has the chance to help a client select a site, though I did have that fortune with my current project near Madrid and it has helped us to settle on an absolutely magnificent piece of golf suited terrain. I think it's natural for the most part, but who can tell!
Melvyn, I agree entirely with you about the need for a course to have a spirit or soul, but I believe you can create that. You just have to be very good at the task. I agree though, there are far too many 'soulless' golf courses, which often times are also those that have cost the most to create...