Perhaps you could help to elucidate manually or with a link, what the advantages of storing the layer as a different color space provide?
In context of Krita, you can use LAB layer in RGB color document to gain access to filter options you normally wouldn’t have. For example, you can use two different layers where they are the same and one of them is essentially converted into LAB, and then you can use LAB color adjustment curves as a filter mask or modify alpha based on LAB as a filter mask. I used it a bit for editing pictures. The only program I know that can does it without workaround is literally Krita and Photoflow. That is it. So, I don’t think it should be implemented into ora, but throwing this out there.