Dorothy's story idea revisited: shifting POV

This is going to be a bit more brief than is typical for me, but I do have to get some sleep soon. So in brief, I have a question regarding POV.

Dorothy's recent story idea was written in first person. I discovered, however, that for the story to end as I want it to, I must write the story in third-person, omniscient narrator POV.

What I thought of doing was this: I'd use the main character's diary as a framing device. Those would be written in first person, while the narration in-between would be "omniscient narrator." The diary would be in italics, separating it from the main story. Would that work?