The webServiceMethod template generates a "local object" called xml.
In your case you would need to
a) tell the webServiceMethod _not_ to generate the declaration and
b) add the xFiles Local object extension, being sure to name the object there
xml
(NOT MyXML1)
Then you will have access to all the derived methods.
The switch (for (a) above) is included in 8.18
Cheers
Bruce