it would be very neat if that could be inherited into the config via the template on a host by host basis, although not sure how at the moment.
Michael seems great about accepting patches that improve the project, you might take a stab at it once you figure it out.
This was the original intent behind --dhcp-tag, which you can use to write your own templates that do things on a particular subnet by subnet basis. It's a bit of a hack though as it doesn't really model anything, it's just a field to key off of.
Having the next-server specifiable on a per-network-object-basis is probably what we'll want to do for 2.0.
Indeed, help in the development of that is very welcome.
--Michael