Megami Magazine 2011-03
From Puella Magi Wiki
Interview with Gen Urobuchi
At this point the opening looks like an amazing fraud (laughs). How they're not taking the decision to become magical girls lightly adds weight to it. After all, it's the story until they make that choice. The viewers might be confused by that, but it's possible because we don't need to sell any toys. If this were a project with many sponsors, we'd get slapped around if we didn't make her transform in the first episode (laughs). But since we're not stuck with that type of project, we'll just do anything we can get away this time.
She appears as a character that covers values of battle after the premise of the series has been established. How her sense of values differs from other characters, as a character that changes the viewpoint [of the premise], that there's someone with this way of thinking. After Mami's death, the viewpoint is changed to Kyouko; the way each Mahou Shoujo treats her is how each character's nature becomes clear.
Homura's position is that she's another veteran Mahou Shoujo apart from Mami, since it's clear that she knows something Sayaka and Madoka don't know. After Mami's death, she's going to become the one who holds the key about various mysteries in the show. She's going to be the one that pulls out the truth together with Kyubey.