Until recently I did almost all my processing in Lightroom, but a combination of its increasingly poor performance and lack of tooling (luminance masks for example), has lead me back to giving Photoshop a much greater role. Although I do lens correction, global tone-mapping and capture sharpening in Lightroom, I then switch to Photoshop. I generally work towards a black and white image and prefer to do the conversion as late in the process as I can. This means I need to do it in Photoshop instead of Lightroom, but Photoshop's B & W adjustment layer doesn't feel as useful as Lightroom's which adds two extra channels - aqua and orange - to Photoshop's six.
Is there any way to replicate Lightroom's eight-channel approach in Photoshop?