If you want to run LegacyIOAHCIBlockStorage from /E/E without -f you'll need to satisfy it's dependencies too. I'm not in Leopard now but a google result tells me they are IOStorageFamily and IOAHCIFamily. So you'll have to copy those to /E/E too. Then it should be ok.
I've been trying this method for making LegacyATIRadeonX2000.kext with no success so far,
left only the info.plist in the kext (which works fine in my extension folder, just added my device id).
I think it's an issue of dependencies as you mentioned but i can't seem to find what other kexts I need.
maybe you have an idea?