Here's an update.zip template that lets you flash a kernel to ANY ROM, regardless of ramdisk. How it works:
updater-script runs and extract the boot.img from your current ROM.
It unpacks the boot.img into kernel and ramdisk.
It repacks newboot.img with the new kernel and the same ramdisk.
It flashes the newly created boot image.
If you distribute your zImage and tiwlan in this format, it will work with *any* ROM. No need to repack per ROM anymore!