The conclusion of my opinion about abcl-jfli contrib:
1. Worth to have. One of the advantages of jfli which has not been mentioned here is that it's portable: the java interacting lisp code based on jfli will work on other Lisps, not only on ABCL (jfli home page for more info about it: http://jfli.sourceforge.net/)
2. About new-class, as I see now some efforts are needed to bring it back (not sure how difficult it is). I personally am not able to be involved into the development in the foreseeable future.
If no-one can fix it now, there is no sense to delay the progress by the new-class issue: if there is a ready to use abcl-jfli version without new-class, we could create a contrib in this state, and maybe file a track ticket for new-class support.
Nothing prevents someone to add the new-class support later.
Best regards, - Anton