If there isn't a better method available, you should be able to do this the hard way, by editing the cr2.  You would want to go into the "channels" section for your actor, then go into the "joint[xyz]" and "twist[xyz]" entries and swap around their weight map references, under "zones", then "weightmapzone".  Switch around the "mapname" listings.  That should allow you to change the weight map associations however you require.

Whether the re-associated maps would handle as intended, however, I don't know....  :unsure:

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Cage can be an opinionated jerk who posts without thinking.  He apologizes for this.  He's honestly not trying to be a turkeyhead.

Cage had some freebies, compatible with Poser 11 and below.  His Python scripts were saved at archive.org, along with the rest of the Morphography site, where they were hosted.