He! I recently went into some “beautifull messes” when trying to touch mesh’s polys AFTER having shapekeyed them. For artistic fun and volontary uncontroled animations, it’s great… otherwise, it only means auto-sabotage.
The only way i see by now, would be to work on several copies of a mesh and bring the shape keys gradually to more complexe changes from one copy then the others. In postcompo, you can then replace the rendered sequences and simulate the transformation of a same and unic object.