Try to use "live-persistence.binds", just specify /etc/udev/rules.d/ in that file at build time.Thanks a lot :) Seems to be a clean way to achieve my goal. And I could use this to put e.g. /var/log on a tmpfs. Thanks again :)
It seems like 08persistence_excludes is broken. I opened a bug (523070). My current workaround is to only define... one directory ;)
Regards, Cyril