Not a very good answer.  Makes maintaining the WSDL a very tedious prospect.
That is a lot to give up if all you need is to expose the web service
through a port mapping web farm.  Fortunantly, I found a much better answer
by calling MS support.  I'll share it here since I found no help on the
internet.  Hopefully, it will others who have this kind of problem.

The solution involves creating a Soap Extension Reflector.  Something like
this:

public class WSDLAddress : SoapExtensionReflector
{
 bool bFirstTime = true;

 public override void ReflectMethod()
 {

  if (!bFirstTime) return;
  bFirstTime = false;

  SoapAddressBinding sabAddress =
ReflectionContext.Port.Extensions.Find(typeof(SoapAddressBinding)) as
SoapAddressBinding;

  string sPort = ConfigurationSettings.AppSettings["myPort"];

  UriBuilder uriLocation = new UriBuilder(sabAddress.Location);
   uriLocation.Port = Int32.Parse(sPort);

  sabAddress.Location = uriLocation.Uri.AbsoluteUri;
 }
}

You also need to register the reflector in your web.config with something
like this:
<webServices>
 <soapExtensionReflectorTypes>
  <add type="WSDLPortMapper.WSDLAddress, PortMapperAssembly" />
 </soapExtensionReflectorTypes>
</webServices>

The interesting thing to note here is that when the reflector runs you have
control over many asspects
of the WSDL generation.  So this technique may be used for other tweaks on
the WSDL.

Enjoy!

Ray