I just turned off NWAM so that I could get IPv6 auto-configuration working. That part's easy:
touch /etc/hostname6.interface
svcadm disable network/physical:nwam
svcadm enable network/physical:default
The hard part is that this broke IPv4 DHCP. The trick turned out to be simple, but take a lot of playing to find:
touch /etc/hostname.interface
touch /etc/dhcp.interface
This solved errors like Failed to configure IPv4 DHCP interface(s): interface
and in.routed: route 0.0.0.0 --> gateway nexthop is not directly connected