I have some fixes for linux receipt to build with tazwok. I just need to know if your chroot has tazwok installed by default only so stuff like this will not effect tank.
[ -x /usr/bin/tazwok ] && report open-bloc
Cause to me that should fix your problem with linux receipt since tank shouldn't have tazwok installed by default if your using cookutils now. Things like this would be needed anyway so linux receipt works with tazwok..
Also about cooking aufs before linux-module-headers. Its is a bad idea. Linux kernel needs to be build before aufs is build cause it needs to use the linux-modular-headers package your building. NOT the one from the web that could break it anyways cause the config for the kernels could be different. Like when you changed the arch to i386 in the kernel config. If you use the older linux-module-headers you will be compling aufs for the older config set to i486. You also can't cook aufs in linux receipt when kernel gets updated. You will just be building aufs for a older kernel that will have to be build again anyways.