Comment 6 for bug 1519733

Grab the /EFI/BOOT/bootia32.efi binary from the zip file I posted (it will allow the ISO to boot on 32-bit systems). You can have both bootia32.efi and bootx64.efi on the ISO, they don't conflict.

Once the the two binarys are on the ISO it will work. Obviously you will need to include the UEFI 32 Grub packages in the pool folder for offline install. I posted the packages you need in the other post.

As for startup.nsh it's not really needed. Not even Ubuntu include it as a it only effects a handful of systems. But if you want to include it I posted a snippet of code that will look at the system architecture and add the correct values.

http://pastebin.com/AZ0MXe9G

Just add it to the /usr/share/ubiquity/apt-setup file.