Yes. You can do it, for example, copy the strip you want to nodegrade, import it in the image editor, feed to the nodes, check render composition and create the grade you want. Return back to the first scene and replace the strip with a scene strip of the new created scene. Then you render and get the node graded scene. Obviously this is a lot of clicks and will be fine to automatize…
If you grade the entire sequence and only uses a part (ie from 100 to 120 fr) in the master timeline, i suppose blender only render through nodes this 20 frames.
But the difference is that node images are feed by image datablocks, and sequencer are strips created on the fly, not linked to datablocks. Thats why i am looking to merge images_to_planes with the footage importer, and make an operator to instert the image datablock to the timeline. If all your clips are imported as image datablocks you are (in theory) able to load them in the timeline or in the node editor, you can view all of them in the image editor (and maybe use texture painting like a garbagge matte). Also you can imagine the 3dviewer like a clip viewer like in apple color, with a plane for each clip, with texture assigned to that clip, where you can order clips by similar colors or shot fields to grade.
Thats what i want to achieve with the Scene per Clip workflow. If you get the structure of the script you only need to load the image strip through nodes and replace in the timeline with the current scene. Then you set in and out, and reimport to the master timeline. It should work.
Now i need to test if all of this stuff is true… XDDD