Hi laurentsd,
We found a solution that is to "inline" (or nest) the library inside our own plugin bundle by following these below steps from this discussion https://communities.vmware.com/thread/444903 (The reason, as you said, that we don't want to modify 3rd party libraries that are not OSGI enabled, and deal with Import-Package):
1) Package our plugin-service.jar to include the dependent 3rd party libs at the root level of the .jar file for instance.
2) Add the following line to our Java bundle's manifest: Bundle-ClassPath: ., my3rdPartyLibrary.jar
Actually we use this solution for bundling our plugin with them successfully ouside of Eclipse, but how can we start virgo server with the 3rd party libs in Eclipse if we want to debug our plugin Java service?