I just did a little test using M2P4Lo:

I switched the rigging method to "Poser Unimesh"

The Poser 11 Genital switch still worked. (It simply swaps a genital hip + genital geometry with a non genital hip geometry)

Then I selected one knee and turned the falloff zones of the knee ONLY into a weightmap.

And re-rigged it using the weightmapping tool.

The Poser 11 Genital switch still worked.

So, as long as the bodypart that is going to be switched is NOT weightmapped, everything else CAN be weightmapped.

Just do not hit the "Merge All Zones To Weightmaps" button but convert the falloff zones one-by-one inside the weightmapping tool.

*

Now, of course, the hip/buttock resp. the hip/thigh joints benefit tremendously from weightmapping, so NOT weightmapping the hip actor would be a bit of a problem.

So, to add a tail, I would just create a "secondary hip" part that either connects with the tail or acts as a plug to cover the hole in the main hip if the tail is not needed.

This allows the main hip to be still weightmapped.

And only that secondary hip part stays non-weightmapped and can therefore be swapped.