I think you're mistaken.... or reading some obsolete web page. Where are you getting your information ?
Every recent VIOS fixpack (containing the *.bff files and other required filesets) has been available for anonymous FTP download.... just follow the download instructions & you should be good.
Well, with servers in remote locations, all the more reason to download the individual bff files & related filesets to a central AIX server..... update the .toc, export the directory.... NFS mount the directory on your remote VIOS Server..... and install the fixpack. I do it all the time. No need for an ISO image.
But, I'll respect your method. You gotta do what works for you. This leaves you with only a few options:
a) live with the 4 x CD ISO images
b) create your own DVD from a downloaded fixpack
c) wait for IBM to fully convert over to DVDs. I seem to recall a notice that they intend to change their s/w distribution to DVD only.... so I'm sure VIO fixpacks will eventually convert to DVD as well. Dunno when that will happen though.
