After some fiddleing with the MacOS X package format I got working packages and an umbrella .mpkg to install all of the in one fellow swoop. I also got familar with hdutil to put it all into one disk image file. Currently I only got HFS format images working, I was not able to get an UFS image working like for example the ones from Apple. This is probably not important, but I really would like to know what I am doing wrong as the Finder pops up if I insert one of those images I did a newfs on and offers me to reformat that one as the format cannot be recognized.
While experimenting with the packages I did run the GUI PackageMaker quite often to compare what I did in my shell script with what PackageMaker generates. Once I did forget to set the default install dir, which means that it was by default /. The package I was doing did also have bin, sbin, etc and var directories like one has in /, so after installing that one for testing I blew away my MacOS X installation. Oops.