I think the need of repacking and repacked images for every kernel-rom combination is a huge nuisance.
What would be if ROMs would contain their ramdisk on the system partition, and the kernels would just contain a minimal ramdisk that loads the ROMs ramdisk?
My first idea would break compatibility with system recovery zips, so a little modified:
There would be a new "ramdisk" directory on system partition, that would containt all the ramdisk files a ROM should have, except the system folder.
So it would contain:
and so on.
The init in the actual ramdisk would mount system first, and then make the links:
/bin -> /system/ramdisk/bin
/etc -> /system/ramdisk/etc
/data -> /system/ramdisk/data
and then we would include init.rc from /system/ramdisk.
Of course all the ROMs would need to change, but after that, there would be no need for repack. Also for the old ROMs, factory ROM, some could still repack.