Why would one want such a thing as /dev/cuaXX ? I've had the same problem
   recently (modem, xntp-refclock), and found ttyflags(8?), which allows you to
   configure /dev/tty0? as a dial-out device at boot time (well
   basically). Adding "softcar" to the appropriate lines in /etc/ttys worked
   perfectly for me, and this solution is obviously architecture-independent.
   (this is current-users, not port-i386 - soapbox omitted :-)

ah, but until recently *only* the i386 port actually used
the information in /etc/ttys .. now the sparc and sun3 ports
have it available, but, to my knowledge, none of the others
do.