Shadow catcher material for Image Based Lighting setups

I’m experimenting with Image Based Ligthing from HDR images and with backplates to see how realistic I can get it to look.
I’m using a movable skylight with a cube map, and a movable Directional Light.
I feel that the results so far are promising.

I’ve adjusted a plane to the orientation of the backplate image and have a mesh of a car standing on it, oriented in the same direction,
and I’ve adjusted the directional light to cast shadows in the same direction as the sun in my backplate image
(might not be exactly right in my screenshots, but close enough for now), but what I would like (and don’t know how to do or if it’s possible in UE4)
is having the plane the car is standing on be invisible, except for the shadows coming from the directional light; a shadow catcher plane so to speak.
Is this doable in UE4? If so, how? If not, is this a feature you would consider implementing? It would be VERY helpful for product presentations etc.
I know that it would be easy to put it together in Photoshop, but it would really help to be able to do it inside the engine.

In short, more or less a combination of the shadows from image 1 and the whole background from image 2.

Surprised this is not a ting yet in UE 4.

UE Devs , show some love for people coming in from VFX / compositing side and make this a thing :o

I’d like to know if it’s possible aswell!

I’m interested in trying to do some kind of matte painting with unreal and photoshop too!

Or something like this guy did… !

I also need this!