Dave:
Absolutely, the client has his "wish list" and we usually do our best to incorporate what we can as long as it doesn't mess with the site.
At Sebonack, Michael Pascucci was spending $100 million of his own money on the project. You don't think he might want some say in what he got for that? He told me there were three holes he'd like to see something like in the finished product -- the fourth at Bethpage Black, the twelfth at Augusta, and the eighteenth at Muirfield Village. (That's his list of favorites, not mine.)
Fortunately, he told me that after I had already done a routing for the course. We had to put a pond somewhere [two, actually], so his Augusta-like hole (not in plan view, just a tough par 3 over water) became #8. We convinced him that the ninth hole was enough like the fourth at the Black. But the eighteenth at Muirfield Village we just forgot about.
Interestingly, when I saw Nicklaus' early routings for the course afterward, they had tried to include the par-3 and the MV hole as the 17th and 18th, and to design the rest of the course around it. And I think that's why Michael was not pleased with their routings -- not because they were pandering to him, but because they didn't find the best natural holes first.
As to your last question, no, I've never been told we had to get the course up over 7000 yards. But when Beechtree came out at 6,999 yards (no kidding) the client did decide to build a back tee on the 18th to get it up over the magic number.