Official DVD-1-ISO/CDROM preseeding from preseed.cfg stored on USB/HD without remasteringDVD (also load firmware)

[Veek M <vek.m1234@gmail.com>]

1. How do I pre-seed the official ISOs without re-mastering them? The
idea is that I have a USB stick that boots GRUB via
sdb3/FAT(ISO+/boot+preseed.cfg) and then I feed the preseed via
menu.cfg-->file=(something-magical)/files/preseed.cfg

Currently I pass the preseed params via the USB/Grub:
menuentry 'CDROM Quick Rescue' {
    insmod iso9660
    insmod linux
    insmod pata
    set prefix=(ata2)
    set root=(ata2)
    linux /install.amd/vmlinuz locale=en_IN.UTF-8 keymap=gb
rescue/enable=true hw-detect/load_firmware=false netcfg/enable=false
netcfg/hostname=deathstar
    initrd /install.amd/initrd.gz

But I cannot load firmware this way! And it's not the easiest to
alter. Once I load pata, my (hd0,msdos2) disappears - how do I prevent
this and load firmware/ .cfg files.

(additionally is this module behavior documented somewhere? how do I
read up on the various modules and their interaction - ahci, pata,
setjmp)


2.
menuentry 'Debian 9.5 Stretch ISO' {
    loopback loop $iso
    linux (loop)/install.amd/vmlinuz iso-scan/filename=$isopath
shared/ask_device=manual shared/enter_device=$isodevpath no-prompt
no-eject locale=en_IN.UTF-8 keymap=gb file=/hd-media/files/preseed.cfg
    initrd $isopath/initrd.gz
}

I basically downloaded initrd.gz from some random website because
google told me that it had iso-scan and could mount hd-media - true to
form it works but, there's no checksum/hash/signature to verify it. Is
it possible for me to mount /hd-media and run iso-scan from the
OFFICIAL debian ISO? Can I achieve the same
results/mount-loppback+preseed-from-USB-partition using the official
DVD1ISO?