How to add "skin" to a Voronoi shape?
I posted this to an Autodesk forum, and a fellow named "MagWeb" proposed the following solution.  I have not tried it yet. 


  A possible workflow depends much on the overall shape of the voronoi
  object:
  If it's convex  all over (like an egg) or convex and planar (like a
  cylinder) e.g:
  
  
  SelectAll (Ctrl+A or Cmd+A on MAC)
  Run Edit/FitPrimitive and set its PrimitiveType to ConvexHull (CreateNewObjects checked)
  Run MakeSolid on this hull object and set its SolidType to Accurate. Accurate enables the OffsetDistance slider. Pull it down a bit and hit
  update. You want to get a result intersecting but showing the voronoi
  object. If needed adjust the offset. Finally accept.
  Now activate both the voronoi and the MakeSolid result and run BooleanUnion
  Show the FitPrimitive object again (MakeSolid did hide it before) and run MakeSolid again in Accurate mode. Now set a slightly bigger
  offset as you did before. The difference will determine the "lining's"
  thickness. Accept
  Activate the BoolleanUnion result first and the last MakeSolid result and run BooleanDifference to get a hollow object. You might use
  another intersecting object to bool-off an opening the bottom.
  
  
  Harder but doable with a different workflow on an voronoi object
  owning concave regions...


edit

Having run some trials, I can confirm this works for simple convex objects. If there are concavities, most likely the source shape needs to be chopped into sections each of which can be treated as convex.
 I played around with Meshmixer's "apply pattern" functions with limited success.  I could get a form-fitting pattern shape but with a rather uneven surface. Some fine-tuning of the pattern parameters may help. Note that the new shape tends to be as thick as the original voronoi object, so it may well be better to do something like the following:
1) create a duplicate of the original
2) shrink the duplicate by a few percent
3) align the two objects to a common origin and take the boolean difference to create a thin-wall version of the original.
4) Build the pattern object based on that thinwall object.   

edit number 2

I succeeded!  For those who care, I took an open Voronoi glasses case and put a skin inside to protect your glasses.  See this Thingiverse item