I realize this has been addressed before, and back then, the general consensus was that cloning was better. However, I'm seeing a lot of suggestions on this thread for "make this editable, make that editable, can we have an item that can do X?" and so forth and so on, so, I'm thinking it'd be a lot less work for George in the long run to simply expose all of the internals of an object definition in some form, and come what may. Dungeon designers can combine properties to their hearts' contents, and produce all sorts of bizarre objects that don't really follow the rules-- flexibility at the price of usability, I'd imagine.
Cloning is somewhat the RTC equivalent of ADGE and such tools, this would be more like hex editing.
The kind of person who would actually go nosing around in the nuts and bolts of an object probably doesn't strictly need the editor, so support could probably be limited to the txt file (as long as the editor was able to load and save the new objects, that is!) Indeed, it'd be more like "programming" than editing, so maybe a text interface would be cleaner, anyhow. Of course, if a sane interface to the editor is possible, I'm not opposed, either!