What to put in /usbkey/config , or in init service, so that default route for global zone on SmartOS uses particular gateway on the LAN and not the slower one..

don't know for sure how to do that from /usbkey/config but the file that controls the default router should be /etc/defaultrouter IIRC ; I only give my global zone access to one of my networks (the sub-zones have a richer network stack)

or put another way, my global zone is only plumbed on the my mgmt network and doesn't expose itself on all the available networks that the created zones will have access to