Michael:
There have been many architects, ODG's and modern day architects who have incorporated them in to their work, from what I have seen they really fit in and are quite pleasing to the eye. IMO, I think they should be incorporated into play and maintained as a link to the past and as an indigenous landscape feature. They can with careful planning during routing become key features in design--a great bonus. A few years ago, I found a couple stone walls that were buried which crossed in front of a set of tees at about 50 yards. In our master plan, I recommended that they be unearthed so in view looking back from the FW to the tees, you would see the stone. The members loved the idea. I believe Tom Doak kept some stone wall remnents in his project in Scotland, The Renaissance Club.
Heck, there have been architects who kept old stone walls from buildings right in the playing corridor--hey a hazard is a hazard, no one ever said it had to be a bunker, a tree, water, a ditch, etc., if it works with the design and it is pleasing to see, why not keep it. It really isn't much different than keeping boulders, large rock outcrops and such that we see out west, or across New England. If I remember, I think Shaker Hills near Stowe, Mass has outcroppings in play on many holes. Blackstone National also has many such features--I think they can be very effective, but they can also be over used, like anything else that looks cool.