YES!
I got it to work! It's not actually a naming convention issue, but a name parsing (I think) "bug". Wouldn't you have renamed the spider wraith variantes like c_spidwrai01_cl_body01 (using of course c_spidwrai01_cl_extraA01 abdomen), c_spidwrai02_cl_body01 (in relation with c_spidwrai02_cl_extraA01) by any chance?
That's what I did, naturally, and got nothing (not even the stock textured spider). Checking the length (I wouldn't be surprised if the 32-character limit applies there too), I was certain it wasn't the reason, and decided to use a totally different name to make sure it was not some name conflict problem.
As it worked, I tried again: no variantes as soon as there was a digit in the name. I replaced 01, 02, by a, b and got this:

top: wraith spider with the stag beetle colors
left: stock wraith spider
right: wraith spider with Krystal texture
The problem I see is that MDB Cloner alone will not suffice, as the name of the mesh needs to be changed (otherwise, all versions will use the standard extra mdb: that explains why all the stag beetle mandibles use the same color.).