That's a good start and I wish I had thought of it when I first created the pain rules
Perhaps addiction would make tasks one difficulty level harder if not satisfied?
However I'm not in favour of constantly shifting the Difficulty level because the change in Difficulties is so large at times.
At the time I toyed with the idea of having dice modifiers impact certain rolls. It was a simple addition/subtraction from the result using relatively small modifiers e.g. a person using a power tool they were unfamiliar with suffered a -1 to the result of their Task check. A negative impact but not so heavy as a complete Difficulty shift.
And it also works to the character's advantage sometimes with a positive modifier making the chance to pass a Task check a little bit easier but not so easy as a full Difficulty shift.
As an aside, I'd encourage people to add tags to this thread to make it easier to find in the future. One person can only add two tags per thread so I think we need to add tags such as "water", "food", "pain" and the like.
I've taken the liberty of adding "rules" and "survival" tags but we definitely need others added.