The only distiller doing this is Jim Beam with their Distiller's Masterpiece. I forget how they handle the "Is it bourbon?" question, but they finesse it in some way. My feeling is that once something is bourbon, you don't make it un-bourbon by doing something else to it, much like making a mixed drink (i.e., adding ingredients). It's sort of bourbon-plus.
I really don't think something like this will catch on, though. Because bourbon is so flavorful, it's hard to think of a "finish" that would really complement it. In contrast, I'm thinking of that Canadian whisky that is finished in sherry barrels and all you can taste is the sherry barrel, since the underlying whisky is so flavorless.
<A target="_blank" HREF=http://cowdery.home.netcom.com>--Chuck Cowdery</A>