What would be interesting is if Epitaph 2 ends with Caroline's complete and total failure to salvage the situation after revealing that it's all her fault to begin with.
Her plan was essentially Blow up Rossum, ?????, Profit. There was no thought behind it nor any consideration of the long-term consequences of her actions. Really, Caroline reminds me of the stupid animal rights activists who always release the plague-monkey at the beginning of any outbreak movie.
I think that's supposed to somewhat be the point behind Caroline, she saw them as evil and figured to stop them, she needed to start blowing up their buildings. I think Adelle herself said that Caroline was dangerous because she is (along the lines) an idealist (or was it optimist?)
I think, ironically, it is sort of required by the character development for Caroline to end up being a less complete person than Echo. If Caroline was fully revealed to be the better person, then Echo is stuck with the right thing to do being to allow herself to "die" and Caroline to fully come back. Which, would have been one way to do it.
But, Echo is clearly our heroine, and even if Joss doesn't like happy endings, he DOES like his central hero remaining the central hero (even if dark and tortured). So, Caroline had to end up being a less impressive person who we don't really want back, in the end.
It is possible though that Epitaph 2 will fully explain that Caroline has fused with Echo over ten years and transformed into a more mature version of herself.