As for the JCM's, even IF you could port them over, they'd be useless in Max.
V4.2 was rigged to make heavy use of magnets, which MAX of course can't "read", and her JCM morphs are matched to such a "magnet enhanced" rig.

So, if you loose the JSM mags, you have to remove the JCM morphs, too, and start from scratch.