Mazak,
I dont understand your specific problem either - I just used 'edit all materials' on an object that has 41 materials, I just changed the bump depth on all of them. Then I looked specifically at several of the material and they all still have their own texture map, the only thing that changed is the new pump depth.
However, the options with this are limited - you either edit one by one or all of them. You cant edit just all the sails but not the body (or at least I dont know how to do it)

I think the OP referred to something else, and I'm not sure this could be done with python.
The problem is :
lets say I  have a model of a house and it has 3 materials: walls, windows and roof.
I would like to have 2 sets of materials
A. Poor man's house: brick walls, transparent windows and red tiled roof
B. Nobility house: Marble walls, cathedral glass windows and gold roof.
I could save 2 different objects which have the same geometry but different material.
But it would be nicer if I could save just two sets of materials, and when I have the object I can apply  material set A or material set B. It will automatically apply the correct material to each of the 3 material groups.
This is analogous to what poser does - If you have a new texture for a character you dont have to apply a texture to each material group(ie head, limbs, etc) individually, you just apply the whole set.

So is that possible, Impish? I havnt discovered a way yet.

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