You can actually extract the System images.
If you open up the PDA file with Winrar, you can extract the system file, which contains your /system. From there you can use unyaffs to extract it to your computer/phone. You can download a compiled windows version unyaffs from this site:
Android programming
That will allow you to extract. I was working on this while trying to figure out some things on the original method to get the Galaxy 1.5 firmware working.
However, I am uncertain how to then recompile it back to a compatible system file. However I would assume that you could use the Yaffs tool to recompile though I am uncertain as I have not tried to recompile a system img.
I do agree with NU that it would probably be easier to file his method into compiling a flashable image though.
EDIT: I take that all back does not work with the new system from BH_Man... Sorry guys incorrect!