Feature Request: Preserve Underlying Transparency

[jhughes696]

Is your feature request related to a problem? Please describe.
I'm always frustrated when I need use multiple animated layers as a source for an Alpha Matte. So someday, it would be amazing to have support for Preserve Underlying Transparency. It takes the combined alpha channel of all the layers below and clips the selected layer inside this "composite" Alpha channel of every layer below.

Describe the solution you'd like
Add support for After Effects native feature "Preserve Underlying Transparency"

Describe alternatives you've considered
Sometimes (in the case of this character animation) you need your selected layer and the AlphaMatte source layers to be parented to the same null. In this example, I need the shadow layer AND the character's layers to be parented to the same master nulls for the Body and the Scooter. Usually, I would precompose the character's layers to create an animated AlphaMatte; but pre-composing the animated source layers means they can't be parented to the Body null or Scooter null in the main comp. So it would be more efficient if I could keep the shadow layer and character's layers in the main comp, place the shadow layer on top, and turn on Preserve Underlying Transparency in order to matte the shadow inside the character's layers below– all whilst preserving the parent chains to the Body null and Scooter null:

Additional context
Here is another example along with an AE test file:

[calda]

Thanks for the info -- I'm going to convert this to a discussion for now since this is a brand new feature that doesn't exist on any platform yet