How to show back layer without scrim on front?

**Is your feature request related to a problem? Please describe.**
I have a situation where I want to show some of the back layer, while allowing the user to interact with the front.

like this:

but of course I also want to retain the default behavior for other situations: like when I'm showing navigation options.

**Describe the solution you'd like**
So I'd like to be able to call a sister function to `.revealBackLayer();` or even something like this `.revealBackLayer(activeFront: true);`

**What I'm looking for**
How would you go about implementing this? I'd be happy to implement it if you guys are busy, because I want this feature now. But I'd like some pointers or hints as I don't know the code base well. What steps would you go through to implement this?