Well, OK, the phoneme example was just a ferinstance.
For the record, as far as your other examples, yeah, I wouldn't morph those things as a whole, and would only do small parts. That's how I've always done it anyway.

But as far as mouth opening, I think that's a little different. Forget about phonemes, but I would use an open mouth morph as a base for, say an open wide morph or a scream morph or anything similar.
My point was that if I already have an open mouth OBJ file and all it does is open normally, I'm going to use it as a base to make an open wide morph, not completely redo it from scratch.