Feature Request: Projection Brush

The noise brush is awesome. But wherever you paint the height keeps on accumulating while you drag, especially the parts which aren't in the brush center accumulate. Would it be possible to have the noise overlay on the terrain and the brush act as a mask?

Example: See the dark parts in the noise image which might be a river. I'd like to overlay that to wherever I want on the existing terrain, possibly resized and rotated, and paint the dark area. The existing terrain should be modified and the river carved in while ignoring the parts that I didn't paint on.

 

This has been a huge pain point for me too, there should be simpler ways to stamp terrain