Hi @kenvandine,
I am not finding any supported category livefs-editor can fit, and also it seems some of the existing supported interfaces should be able to help with the needs you have described? such us: mount-control (to mount filesystems), personal-files/home/system-files/removable-media (to locate user content to be copied into the ISO, which should be stored in typical locations). Can you please also list which are the hosts commands this tool requires? Maybe those can be staged or even shipped inside the snap?
I am pretty sure you probably already tried those, but asking just in case this tool can be snapped with the least privileges possible.
Thanks!