If managing versioned module dependencies with Jigsaw is anything like OSGi, you really don't. I haven't read the former's documentation yet, though.
Many people were frustrated with OSGi because it explicitly made modularity up front and centre, and the majority of developers didn't want to worry about it. The modularity of Jigsaw - including different classloaders for modules - is pretty much exactly the same as with OSGi. The differences are largely syntax and lack of versioning at this point.