P: Motion blur mask option for lightroom

I would like to suggest a mask feature that is related to the motion blur filter in photoshop.

Many photographers need to blur faces or create a sense of movement on images where it was not practical to use a slow shutter spead.  It would be ideal if there was a blur option in masking...I imagine it would be mostly used with a brush to just place the blur on specific areas (faces, full body images of people walking, riding bikes, etc.)  Many Thanks for your consideration.

[Moved to ideas by moderator]