You know, this just made me think of something.
What if, Walter somehow figured out a way to use the "image" of Charlie in the shapeshifter's machine to re-create Charlie in some fashion? Even a modified/improved version of how the shapeshifters use it.
Not sure if it does, but it seems plausible that the "image" can contain more than just the physical "snapshot" of the person it's copying. Meaning, some brain information can be possibly on there, as well, considering brain patterns are just as physical as a person's skin tone, etc.
I know it falls into the realm of "that makes death meaningless," but if a person dies without a machine like this nearby, I'm pretty sure that there won't be a revival without a clumsy deus ex machina which I'm sure the show won't fall back on; this isn't Heroes. I'm just looking for a way to bring back a character I liked on the show.