Install Grub2 (with EFI-IA32 support) to the ESP partition from within Windows 8.1 (32-bit) - Bay Trail tablet
Found it!
I downloaded the newest Ubuntu (15.04, 64-bit) ISO file, I extracted the /boot and the /EFI folders from the root of the ISO. I copied the folders to my ESP partition, and edited the grub.cfg file as needed (in EFI/boot/), and copied the bootIA32.efi file to the EFI/boot folder.
I now have a fully working 64-bit Grub2 on a 32-bit UEFI BIOS self-contained in the ESP!
Now, if anyone would care to take a look at my other question about Grub2, that would be fantastical.