^ actually, I don't feel like underestimating the importance of Madoka's wish changing the fate of others. She doesn't undo the system because first, God knows how it would affect the history (remember Ume-sensei's yonkoma on the matter
), and second, she respects the wishes all magical girls put their lives on the line for. And sparing the indignity doesn't quite describe the opposite: in addition to losing every trace of conscience and humanity and becoming a living web of insanity and despair, a witch can potentially take all the good things the puella magi did and throw them out the window by causing as much grief and demise as the girl once averted. She can even ruin the wish itself in worse cases. Imagine Octavia were left alone; will you guarantee that Kamijou would never be among those falling prey to her someday? There's no sense in saving the day from Godzilla if you become one and ruin the city yourself (figurative as the example is, that's pretty much what the timeline from Madoka's dream was about). Puellae magi give up a lot in exchange for their wish, but with the new system, they can at least live their lives with a meaning.