Jason:
The first two drivers are a good client and a good architect, but presumably you could leave one or the other out of the top five, since the whole exercise is moot unless you are one or the other
After that, the keys are probably
a property with character [including good soils, interesting vegetation, and of course an ocean view]
enough money to do it right [which is not necessarily a lot of money, depending on the property]
a great construction team [incl. project management, shaping, and superintendent], and
a bit of luck that nothing interferes with the realization of it all