In short, the possibility to deform a mesh with another one.
Here's two examples...
- how the lattest Cinema4D R13 handles it :http://www.youtube.com/watch?v=nmu9-fokhf4
- a python script for Maya (there's a video too) : http://www.creativecrash.com/maya/downloads/scripts-plugins/animation/c/jlcollisiondeformer/
Would anyone be interested to talk about / tackle the idea of adding a collision deformer in Wings?