I think that the only way that you could disguise your purchase would use a mix of actions:
[...]
May I suggest an 'out of the box'
alternative?
I believe that you can buy Passports in-person using BTC at some Bitcoin conferences that Foundation Devices attend. If not, they should start offering this option..
Another (possibly illegal) solution: locate an inhabited house in a non-surveilled location (opposed to PO boxes that are often CCTV'd) and use this as delivery location. Either wait there at the day of delivery or instruct the driver to drop off the package & pick it up later. It's a method which has been used for illegal activities in the past, so it should be relatively secure.
Overall, I like that idea, and it does not sound illegal to me - to receive a package at a location that I am at, and either not using my real name or using a fictional name (if the shipper requires some kind of a name?)...
Also if the shipper is willing to ship without either KYC or with minimum KYC that gets removed from their system after a bit of time, that does not sound illegal either.
I am not necessarily wanting to get into any debates, but it seems incorrect to be suggesting that my desire to remain anonymous in receiving a package or the way that I pay for such package would be illegal (or should be illegal..and even if such a thing were to be illegal in some jurisdictions, it does not seem to be the kind of law that would be enforceable, except by tyrants)..
Also, even if such a service has been used to receive "illegal" items or to perform "illegal" products in the past, it seems to me that a signing device does not seem to fit into such a category of something that either is illegal (or should be illegal if some tyrant were to want to make it illegal merely because they do not like individuals having abilities to digitally transact and/or communicate information/value directly with each other and without a third party intermediator).