Sorry, I should have said that it's not necessarily the same animal. The whole mountain of evidence concerns natural languages, right? Do you have any evidence that an artificial language with a self-segregating morphology and a simple sound structure would also go through the same changes?

So I'm not necessarily saying that the changes wouldn't occur; I'm simply saying that we can't reject out of hand the idea that we could build a system where they won't occur, or at least build a system where they would occur in a useful way (rather than a way that would destroy its superior qualities). Where the system starts would determine its evolution; I see no reason why you couldn't control that variable in such a way that it would be a stable system.