Your problem here is that the "hard" parts of the model really should not be deformed (bent), and the areas that are "soft" (e.g. the straps) must be deformed to look natural.  I don't think an item like this is very easy to rig in a realistic way.  You want the hard polygons to rotate with the joint's rotation, but not actually be deformed - typically you'd do this by unchecking the Bend property in the Parameter Dials window, but this will stop the strap part from bending.  I suspect you're going to have to break the item into two separate figures, for the hard parts and the soft parts.

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