I'm not great with shell scripting, but I tried to base it off what is there to keep things sort of consistent. This generates the iso with your chosen username, password, and hostname from arguments and inserts them in to a templated user options file. It optionally includes packages to install from a list formatted the way user options expects it to be formatted. There is an additional script for generating this list from a running system. The idea being that you can create a barebones system, discover which packages you need as you go, then get a list for recreating that system once it is at a stable point.