Mark:
I'm not sure where you were making reference to the work of myself and Mike Clayton above, but here's my take:
I've never done anything to deliberately vary the bunker sand on a course. However, at Pacific Dunes we decided to try using the native sand in place for the bunkers, instead of bringing new sand in to make them consistent [mostly because we figured the new sand would blow away!]. It may be radical but it's also perfectly natural, and no one has ever complained to me about it except where a few bunkers are blown bare down to hardpan.
Since it worked in Oregon, we've done the same thing at St. Andrews Beach, Barnbougle and Ballyneal. We did it at Sebonack also, although we had to screen the rocks out of the sand and then put the sand back in the bunker.
But I don't think I would do it artificially, i.e. deliberately put different sand in some bunkers than in others.