PAM is nasty stuff, I might consider doing something like that with a less potent mite killer but not PAM.

The reality is that a breeder that shipps out a mite infested snake probably won't be bothered to do something like this in the first place Unfortunatly.

With the volume of packages relatitive to the number of reptiles being shipped I doubt that cross contamination is something to be concerned about. Unless both reptiles are going to the same place I can't see them sitting next to eachother and even that is a longshot