What if two packets interact with each other? If you claim a collapse occurs then entanglement could never happen, and so such a viewpoint is logically ruled out. If you say a collapse does not occur but only occurs if you introduce a measurement device, then this is vague without rigorously defining what a measurement device is, but providing any additional physical definition with then introduce something into the dynamics which is not there in orthodox quantum mechanics, so you've not moved into a new theory and are no longer talking about textbook QM.