After a fresh cup of cafe, I think I have a good idea. Why not providing a jetty.xml file in ${SMX_HOME}/etc (like the activemq-broker.xml) and configuring jetty there. And in our (multiple) CXF bundle configurations, we using the already running Jetty as Charles suggested.
Sounds also a good idea for you? I'm working on a default jetty configuration which provides http and https connectors. Maybe this is also interesting feature for the ServiceMix guys... Christian