I noticed that I am unable to use a container that is not named after core containers (cargo-core-container-xxx).
1. implementation - Providing only an implementation without an id causes maven plugin to force the container id to jetty6x and initialize a container classloader for it. Bug is located at AbstractCargoMojo:createDefaultContainerElementIfNecessary
2. id - This only works if the container is named after core containers provided that the jar can be located from mavens artifact factory. Here I also get a custom built container classloader even when I've provided the container as plugin dependencies. The custom build classloader is consulted after maven plugin classloader by the container registration mechanism so this option almost works. Registration mechanism overwrites the registrations that came from maven plugin dependencies with the ones that are coming from custom classloader. Bug is located at AbstractGenericHintFactory:registerImplementation