Thanks for the continued input on this item. We are taking a further look at this request, but it is not currently scheduled for implementation (we work in priority order, taking feedback from customers, here, and other sources).Maxim Doucet commented
also note that you should add "options rotate" in /etc/resolv.conf (this will be preserved even when dhclient is used) so that the OS will try both you DNS servers *and* google DNS serversMaxim Doucet commented
You can already do this by configuring dhclient (which in turns will modify /etc/resolv.conf). The file to modify is generally "/etc/dhclient-eth0.conf" (at least on CentOS)
It is described here: https://cloud.google.com/compute/docs/networking#internal_dns_and_resolvconf and in "man dhclient.conf"
The idea is to use "prepend domain-search yourdomain" and "append domain-name-servers ip_of_your_dns_server" in "/etc/dhclient-eth0.conf"