Rich,
Our course is laid out with two loops, a clockwise circle of three holes,#'s 1,8,9, and a c.clockwise circle of #7 then 2,3, 4 and 5, with #6 ending across the street from the golf shack. Lots of 3 and 6 hole rounds are played by the members because of the layout. They can play combinations of 123, 789, 123456, 189789, 723456 or 789189. Flexibility is really important, as you say.
As for marrying costs to time, the only course I have seen where this works is one very close to my location. Nearly alll of this course is visible from the top of a hill, hole#1, so it's easy to find an open place to start. Once again, the layout makes it possible to see where you can jump around to an open hole. The owner has a few customers, mainly singles whom he charges by the hour. I really believe it's possible at courses like this that have many holes visible from others, will let you jump around and that are not booked soild. The other condition where it may work is as a "premium" to attract early or late players.
The partial round/ flexible price won't appeal to many operators. I do it occasionally with a couple of guys who play on their lunch hour. They pay for nine up front and play a 3 hole loop three times during their work week.