Tattoo placement over skin seams

what I would like to do, is being able to place tattoos anywhere on the character skin like it’s done in games a la “APB reloaded…”, where you can dynamically move the seam for a tattoo layer and even make tattoos that wrap around a limb.
But how to do it?
What I’ve got now is a skin layer and two layers for tattoos. (see material properties screenshot in attachment) Everything works so far, but how to attach a tattoo to a skin over a seam?/How to move the seam to a different position?

Here’s a GDC talk the APB devs did on this topic:

The video for that GDC Vault - APB: Creating a Powerful Customisation System for a Persistent Online Action Game if you didnt find it.