Devices that phone home

For the parts that are imported, a bit of due diligence in verifying the background might determine that much of it is easily upgradeable to GPLv3 (e.g. GPLv2 code where the authors didn't go out of their way to remove the "or later" and BSD licensed code). All of it must be GPLv2 compatible, and nearly all of it will also be GPLv3 compatible.

But hey...

Also, in another sub-thread you've argued that when Linus removed "or later" he was doing so within the terms of the GPLv2. That means that the Linux kernel prior to that point *was* licenced under the "or later" clause. At least, it would be by your logic. Linus argued at the time that he had never meant for "or later" to apply, iirc - which seems weak.

Basically, it seems like you could take an older version of Linux and make it GPLv3, given what you say. You could then contact contributors after that point - which seems like a *much* easier job given it was done after kernel went to an SCM (and after SCO)...