Trello: New Material Layering System???? Theories, Explainations?

So I caught this on trello

I’m hoping someone would explain what the current proposal is, the intended benefits and/or overall end goal of a new material layering system?
I’m very interested as I’ve been creating layered materials myself I really would like to know what the UE devs from EPIC have in mind, it would be great if one of you guys could drop by and give us a little hint?

For those of us who aren’t working at Epic, what theories do you guys have about what they’re looking to do?

Haven’t heard of it before, my guess is that it would be some way to layer materials that doesn’t increase draw calls since that’s the limitation of the current system.