I have been here many times requesting a rewrite of how spot channels work in Photoshop. For a long time I was thinking along the lines of spot channel layers etc etc. A simpler answer dawned on me the other day, that would probably entail a lot less programming. Why not allow control over any spot channels in a document via a channel mixer adjustment layer? What I mean is, when you added a channel mixer adjustment layer to a layer, as well as having control over the normal CMYK channels, you would also have sliders for any spot colours contained in the document. That way you could have many different layers with masks or vector masks, with total control over which inks would make up that layer. After working this week on another very complex packaging job involving multiple spot inks, and cursing Photoshop's name, this solution came to me in a Eureka moment. I get e*d just thinking about it!