Fair enough. Basically what you'd have to do is configure your host to do IP forwarding (honestly I don't know how this is done on any modern system ... ), then on the DR:
route add default gw 192.168.200.1
echo 'nameserver <some nameserver>' > /etc/resolv.conf
You could put those two parts in the usbnet2 script to avoid rewriting them.
(Haven't tested this, YMMV)