recently learned about the isostick, which seemingly does what it says on the tin; it mounts ISO files from an SD card over USB mass storage
sounds about 60% suitable for my purposes, anyone know of a reasonably available alternative that can handle multi-track or hybrid disc images? preferably with on-device image choosing rather than relying on the USB host
EDIT: to clarify, I have heard of Ventoy, but it's specific to boot images, I am after something more general-purpose and broadly compatible
alternatively there's ventoy, which seems to be a version of this that you can use on any usb drive you like (although not sure if it supports the images you mentioned).
also it's mostly meant for booting install ISOs but i'm not sure if that's what yuo want...