This is really just a hunch. We want to figure out which questions the Debian Installer asks are critical, in order to put together a minimal preseed file. To be perfectly clear: the procedure outlined below is hypothetical. I've never done this.
Get the Debian Installer running.
Go to /var/lib/dpkg/info
.
Grep for 'priority=critical' in *.config
Prowl the *.config
scripts to see which questions are asked with priority=critical