While you will be repacking it
Can you create as well one wit root
you just need to add
su binary to /system/xbin/su
and Superuser.apk to /system/app/Superuser.apk
additionally following two lines to upgrade script
set_perm(0, 0, 06755, "/system/xbin/su");
set_perm(0, 0, 0644, "/system/app/Superuser.apk");