I still prefer the IDE approach, since most of the systems I'd want to do this to are far too old for built-in WiFi... Also, the original/host system would have to have a boot-drive and hardware drivers... and an OS with GUI properly configured, and so-forth... (and have you ever tried to get a random wifi card working in a "universal boot"? Oh yeah, and most wifi cards I've run into can't be hotspots, but I'm old)... and now we're far from the drop-in-and-go system-upgrade I've been visualizing.

BUT, did I mention I'm old? (and so are my systems).

This one, #Pi in my laptop uses WiFi... And, frankly, that does the job nicely in newer systems. VNC, so-forth. I hadn't caught that the Pi and laptop were actually talkin', since there were no wires. How obvious could it be?

Nicely-done.

And, realistically, we are nearing (or even within?) the era where a small SBC might be more powerful than a lappy with WiFi, or bootable USB, and so-forth.

(BTW, I think there's a link in the first log where a Pi was put in USB-gadget-mode as a bootable hard-disk.)