Hi, my understanding is that a single N-400 case outside the 120 days after the interview, this course of action might actually work. However when there is a pending I-751, in general a person can apply for N-400 but it will not be approved until I-751 is approved, and right now it takes around 2+ years to be approved. I don't think someone can apply for I-751 and then apply for N-400 to force I-751 to be resolved. Maybe consulting with an experienced lawyer might be helpful.