I’m concerned with the download size during install, and what will happen with slow connections, or if there’s an error etc.
Official Arch and Manjaro publish regular iso’s with latest updates which is perfect for this, and since its a rolling release things will need to be updated anyway in a day if not an hour. But the install should be very reilable IMO and not fail.
At the very least cnchi could cache the files it downloads on the usb, and on next install it can compare versions and only get updates, or give the option to the user to use the cache. I don’t think this would be hard to do and would be a very nice feature.