i feel like i just read something here about using a second uv channel for mask. like edge mask, wear mask, etc. I have no idea if that is major difference in terms of workflow or optimization, just mentioning because it wasn't already.
the downside to using textures for masks is that you have to do a bunch of UV manipulation and mask blending if you want to avoid repetition. in this instance I'd be inclined to go with vertex color as a base since it allows the artist direct control over where the wrinkles etc. happen. I'd use a shader solution if I…