I recently output a matinee camera animation as BMP. I produced it with a green screen chroma key (also tried with red as green wasn’t ideal). The problem was the animation had no solid colour to remove and the matinee used transparent particles so the green leaked through. I tried everything in photoshop from removing the G in RGB, magic lasso, eventually using colour range to get a selection. However this left out certain particles and the colour leaking still existed. I had to recolour the output by using a colour overlay. This was not ideal but for my purposes this was ok. It was not ok for my perfectionist attitude towards my work
So I propose that matinee recorder output should allow for dead BSP space to be excluded from the rendering and replaced with an alpha channel for export as PNG and/or alpha channel video. It would shave off many hours of post processing work which had to be done manually in Photoshop on a frame by frame basis to get the effects.