When was the first mention by the police that the burglary was staged? Didn't the very first officers think it was staged? If so, do you believe the PP decided from the first to frame the kids?
ETA - How do you know it wasn't staged? Could Rudi have staged it because he had asked Mez if he could come over and thought the other british may have been told by her? He then thought he needed to stage it. Not suggesting it happened that way but it could have.
My thought is that that Mignini and the "real" police came to their idea that the break-in was staged independently of the postal police. Giobbi did not reference them or an insurance fraud in his testimony, IIRC, but did mention glass fragments on clothes, his walk-around of the flat and not seeing glass fragments on the ground, and his "reasoning" that a burglar would not choose Filomena's window as an entry, but rather the balcony window. I don't believe the postal police had the intent of framing Amanda or anyone; I don't believe that their role or competence is at that level.
But if you detect that my argument is, shall we say, a little on the weak side, I would not disagree. I have become something of a conspiracy theorist about the police involvement. I even recently came to the belief that Patrick Lumumba was chosen by the police as a targeted "co-conspirator" of the murder/rape because otherwise his message to Amanda and her reply must be innocent and something of an alibi.
My belief is based in part on Giobbi testifying that the police quickly decided to focus attention on those close to Meredith, and Amanda had the weakest alibi. My extension is that since she had a key, the break-in was therefore staged (in Italian police or PM Mignini logic). I am also of the opinion that Amanda, a trusting and naive young American woman with an Italian boyfriend of about one week's acquaintance, was by misfortune an ideal match for PM Mignini's obsessions.
I should say that because of my technical or scientific background, when I state that I believe something, it does not mean that I am convinced of the truth of my belief. Let's say the belief is a hypothesis which may or may not be reasonable and may or may not be readily subject to proof. Another hypothesis may turn out to be more credible, if additional evidence emerges.
Regarding your alternative suggestion that Rudi (aka Rudy) staged the break-in, again it seems possible, but not plausible to me. There was no independent evidence of Guede and Meredith agreeing to a meeting or date at her place, and her British friends testified they thought they would have learned of any such meeting/date from her, IIRC.