Thanks. Interesting exploration. I think physical isolation of individual qubes is novel and intriguing (see USB Armory). Think of plugging in Whonix Gateway (I’ve had GW get compromised before and had to remake from template).
Discussion about Qubes Air also mentions your phone as a “viewer” of your Qubes running in the cloud. But people think having ownership of the hardware is important. One could have ownership of hardware that comprises a cloud accessed by your phone-viewer. That would be cool.
“Ownership” is more of a legal category rather than a technical barrier, however. Most hacking i’ve encountered is agnostic about the legality. If they can do it technically, then they do. You need a cyber attribution unit and a team of corporate lawyers to enforce “ownership” and then if its the Feds or a Nation State ally or enemy, they can just claim “National Security” and do whatever they want anyway. So ‘lock down’ all of your own hardware? If the software was secure, it wouldn’t matter so much what the legal category of ownership was.
Still, an SBC cluster or deluxe SBC with a top class CPU costing a few hundred rather than laptops costing over a thousand might be attractive as well as highly portable to some.