And it appears, so far, that creating a tattoo a second layer is just this easy.  I'll want to verify that it is backwards-compatible, as I don't know if transparency being swappable between transparency and opacity is a newer feature or not.  I haven't played much with Superfly.  I must admit they named it well, because is, to use an obsolete phrase, super fly!  I also want to verify that it will work on color tattoos.  If not, I will find a way that works for both.

This was done on SASE's (Sabby and Seven) Naisa texture after a quick run through the Python 3 version of EZSkin. (Thanks, Snarlygribbly and Fverbaas!)