As the title says. AFAICS at least some of them are packaged in Gentoo.
I've looked at the way this is launched and given that this isn't built from source, it wouldn't be all that hard to do. I count about 8 jars that could be unbundled. To find these at runtime, the ebuild would need to call java-pkg_register-dependency and create a launcher with java-pkg_dolauncher to replace the upstream launcher.
However, I'm not going to spend any time on this. Java team is exploring a totally new direction where we will lean more heavily on Maven/Gradle to unbundle things but mostly only native code will be compiled and the majority of dependencies won't even be explicitly packaged. This is the only option I can come up with besides total collapse. I'm currently doing research to come up with a proof of concept.