you can't really "change these goals so that they just launch Jetty without running the 'package' phase".
The package phase is a component of the maven lifecycle and the only way your going to get around this problem is by adding functionality to the maven-war-plugin that will keep it from rebuilding the war during the package phase. You can't really slot the maven-jetty-plugin earlier in the process since you can't be assured that the webapp would have been packaged up and deployed someplace initially. And since the plugin makes use of maven's lifecycle to pull out dependencies to monitor and use it would be difficult to try and run something outside of the maven lifecycle and retain the functionality.
As for that webApp argument, I think he is referring to the param on the Jetty plugin, which by default is the location of the war produced by the maven-war-plugin. If your overriding that parameter then you are leaving the maven conventions and are kinda off in your own territory.
I think its a great functionality to add to the maven-war-plugin, but its not trivial really since there is so much in play with that plugin and the various bits and pieces it needs to take into account...which is why its probably not been done yet. That is true for most if not all of the packaging phase maven plugins.
Improvement
Closed
Minor
I'd have hoped that maven would be smart enough not to rebuild the war file if nothing has changed, and one already exists in the build output directory. Perhaps something to bring up with the maven guys?
I wasn't aware of the -DwebApp argument. Can you tell me in what circumstances you would use it?
cheers
Jan