You seem to be asking to do confilcting things...
automated, multi-volume backup with cpio and do it in cron job
...the problem is that if you were to redirect output of cpio...
find / -depth -print | cpio -ovcBK 1200 -O /dev/rfd096ds15 > /dev/console 2>&1
...if you run this from cron, you will not have a controlling tty
and cpio will not be "reading" from the tty you are at.
I might suggest using some other backup utility. Take a look at...
http://www.backupcentral.com/software-backup.html
...you might find somthing that suits you here.