Is the swap partition really required for a live FS CD-ROM?

[Daniela]

Hi all, I'm creating a Knoppix-like FreeBSD release (live filesystem, runs 
from CD) with 4.9 sources. I'm almost done, but I don't know what to do with 
swap. I read somewhere that I must have a swap partition in my /etc/fstab, 
can't this requirement be overridden?
And can I create a vn0 device now, and mount it as a filesystem of type union 
over / so all directories appear writable? If I do this, is there some way to 
save these written files (preferably into a single compressed file on a 
floppy or USB memory stick) and restore them on the next boot?

Please help me, I'm really stuck here.
Daniela