Injecting Jasper parameters into field specifications

I want to have shared (template) JRXML files that work for a variety of XML datasources.

The only thing I know of that might prevent this is that the field specifications would be slightly different.

For one XML file the XPATH for a name field might be:

          person/name/last

For another XML file the XPATH might be:

          contact/last_name

Ideally I could pass the XPATH in as a parameter and have the following inside a fieldDescription tag

            $P{XPATH_FOR_NAME}

But Jasper doesn't seem to support the use of parameters in tags.

Is the some way for me to inject the field specification into my JRXML templates?