Paul Cowley,
Since most bunkers sit below grade drainage is a universal problem for bunkers.
Gathering bunkers will direct more sheet or surface water into a gathering bunker, but, I don't see that as an overwhelming problem given today's modern capabilities and budgets.
Most gathering bunkers that I've seen have had grass walls and flat bottomed sand floors, hence washouts haven't been an issue.
As to seperation, I think the lack of use of older features might offer some evidence. The need to be uniquely creative instead of using templates would be another.
I don't know that I could look at many modern architects and indicate that they have patented holes, holes which they repeat, or repeat with variations in their designs.
Tom Doak,
I think the visibility issue may be one driven by medal play and the quest for "fairness"
One would think that gathering bunkers would be ideal for par threes where an elevated tee provides abundant visibility.
Shouldn't architects, in their attempt to provide a challenge to the golfer create features where "AREA" mis-hit shots are directed toward a more ominous hazard ?
Must every shot bounce straight and true ?