https://fedoraproject.org/wiki/Anaconda/Kickstart#network mentions a --device parameter, but I can't find a field for this in the host creation. Adding this field will make provisioning using multiple interfaces much easier. Adding this could also help with ignoring some interfaces while kickstarting and just be a simple additional IP. The mac address should also become optional if the device name is empty for this to happen.

Something like this: (you might need to figure out something with the gateway because of default linux routing)

network --bootproto <%= @static ? "static --ip=#{@host.ip} --netmask=#{@host.subnet.mask} --gateway=#{@host.subnet.gateway} --nameserver=#{[@host.subnet.dns_primary,@host.subnet.dns_secondary].reject{|n| n.blank?}.join(',')}" : "dhcp" %> --hostname <%= @host %>
<% @host.interfaces.each do |i| -%>
<% unless i.device.empty -%>
network --bootproto static --device <%= i.device + " --ip " + i.ip + " --netmask " + i.subnet.mask + " --gateway " + i.subnet.gateway %>
<% end -%>
<% end -%>