Is there something like cage mesh deform, but instead of the cage being larger, it is smaller than the mesh to deform?
The only similar effect I know is the envelope deform that armatures can have, but ideally a mesh of any shape would emit this envelope.
Note — Not shrinkwrap, I don't want volume loss or snapping to surface.
Adding more detail:
An example could be a Skin/Skull set up. I want the internal skull to influence nearby skin vertices. Shrinkwrap wouldn't work as it would collapse the skin down to the skull shape. I know shrinkwrap has vertex groups to isolate the effect, but that is far more work and this is the best example I can think of.