I have no idea on how to reassemble the pieces into a working bios. It's not just a checksum, that's for people doing SLIC ie replacing or adding stuff at the bottom. A missing table in the middle might cause problems. Isn't there an index too?
Anyway, the alternative hack you suggest would be quite a cool one :-) I didn't know it was possible to change the address of the c&c in the option rom (IIRC, it's like packed in an EFI header, then again - I just don't know which tools to use), but if it's, I'd be quite interested - even more if the computrace protocol has ben reverse engineered ;-)
Feel free to contact me by email!