Ok, so it's about 20 years after everyone else did this (SCO, Linux, BSDI, 386BSD, NetBSD, FreeBSD, even Novell), but at least Sun are now doing it!
Here's how:
# svcadm enable vtdaemon
# svcadm enable console-login:vt2
# svcadm enable console-login:vt3
# svcadm enable console-login:vt4
# svcadm enable console-login:vt5
# svcadm enable console-login:vt6
# svccfg -s vtdaemon setprop general/enabled=true
# svccfg -s vtdaemon setprop options/hotkeys=true
# svccfg -s vtdaemon setprop options/secure=false
# svcadm refresh vtdaemon
# svcadm restart vtdaemon
