Tom,
I've never had that situation exactly, but I have had owners say they want flattish greens, because on the big scale of things, speed of play is more important to them than rankings or awards. In that case, the design program set forth by the Owner would tend to limit greatness, but I can't think of an experience where, with a great site, I tried to dumb down a design. In fact, my premise is usually, the farther you are from population, the better the course has to be.
I have also given consideration to flattening greens (usually in deference to the super) but especially in dry climates, where you can guess that water restrictions will make those steeper contours problematical, as they usually require extra water.
But, lets extend that a bit further. If an Owner said "flat greens" there could be other ways - especially on that site - to create greatness, no? Make them smaller, better protected, whatever and create a different type of challenge than the one we might normally do, or prefer as a gca.
In football, if the run aint working, you try the pass. It can be similar in golf design.