Hi Daniel,I followed your advice and created a git tree for an Ubuntu-compatible live-initramfs:
http://github.com/lcapriotti/live-initramfs-jaunty/tree/masterAlthough I garbled a little bit the commits with my runs of dpkg-buildpackage, I hope you may find interesting patches, such as r/w USB boot disk and some compatibility with karmic - now only lack of any kernel unionfs support is preventing live-initramfs to be compatibe with it).
Cheers Luigi