Just an oversight. I agree it would be nice to have this capability. Can you file a JIRA? If you want to submit a patch for it, that would be great too! :-)
You can find the ticket on the following url: https://issues.jboss.org/browse/SWITCHYARD-921
I will try to make some time in order to submit a patch (as a pull request from what I understood from SwitchYard Development page).
RIght, pull request is the way to go. BTW, here's the commit that added support for the service name parameter on the @Service annotation:
Might be useful as a reference in terms of which files need to be touched.