The way I see it,
The only true redundancy is when you don't have to improvise anything from the environment. In which case, that means carrying your fuel on you. For redundancy I carry at least hexamine, trioxane, and thick peices of rubber. One piece of any of these materials will boil about a cup of water without elevation. For cold weather travel I am looking into carrying a can of Eco Fuel. Supposedly, one can will burn for ten hours.

As far as fire lighting, any number of methods will provide redundancy. Finding dry wood might pose a worse problem in some environments.

Starting a fire is always my last resort for keeping warm. I always travel with the means to provide myself adequate shelter.