I work for a die cast/machine house. One way we have addressed the "different machine" issue (we have 25 machines with varying tonnage classifications up to 900 ton) is by submitting PPAP from the lowest rated machine the die will perform on. Many studies have proven no degradation in product quality by moving the tool to a higher classification of machine - in fact, we can typically improve the quality through differing capabilities of monitoring the shot end.
I can't really address the differing raw material lots except that your supplier should (read "shall") be capable of meeting the material specifications on a lot to lot basis. We alloy our own metal, control it coming out of our Central Melt furnace and monitor metal chemistry in the holding furnaces. When we have the need for a "special" alloy, we buy only from a certified source (whatever that gets us) and then perform random audits on the lots of Ingot.
I completely agree with Roger and Sam concerning you deciding what is a process change and what isn't (however, don't be surprised if your SQA decides to "help" you with your definition). I might be all wet but as I look at the requirement, it is saying that should something in your process change which causes a quality concern, how do you handle the issue? We have a corporate nonconforming material procedure which is supposed to cover any parameter "tweaking". We encourage our operators to experiment (with guidance!!!!) but when experimenting, product must have an NCM tag.
I think I'm getting off base here so I'll sign off. Hope this helps some.
Bill