This can become unwieldy when there are a load of drawings.
Multiple sliders could make this a lot more manageable, in a similar way to pose copier.
e.g. for a mouth substitution, one slider could control the view front, 3/4, profile
another the emotion happy, sad, neutral , etc
and the third slider the actual phonemes.
This could be easily implemented by a naming convention for the drawings, so that they could be sorted into slider groups.