As for implementation, there're a few methods I'm currently considering:

• write a C-program to just do it all, or
• use a shell script, with pipes into /bin/fdisk for the low level details.
• stick /bin/gawk onto the image and use an awk program piped into /bin/fdisk for the low level details.

The first choice means I could take and incorporate it all inside the Hijack kernel, if that turned out to be useful.

The scripting choices may be more work, but are far less opaque in the end (easier to understand, test, and modify).

Cheers