Thanks to everyone who confirmed that Ventoy wouldn't be of use to me, according to my needs But those needs may be changing.
It turns out that my wife's laptop, which I'd thought she killed, was simply a victim of a bad power supply, and a new replacement is arriving today after 10am today. And the new laptop I'd ordered when I thought she'd killed her current one will be here tomorrow.
So after today, that new laptop won't be needed for her, and I think I'll keep it as another spare computer for testing interesting distros on hardware. There may be a job here for Ventoy and the new flash drive after all.