[boost] [smart_ptr] copyable_ptr?

I was wondering if boost has considered a smart pointer that is similar to scoped_ptr but supports deep copy semantics. This would be useful in classes which use the pimpl idiom, as a common way to program these classes is with a scoped_ptr or auto_ptr, but then a copy constructor and copy assignment operator needs to be defined. Herb Sutter worked on an implementation at http://www.gotw.ca/gotw/062.htm, so there's precedent. Is there any interest for this?