From what I think I understand about what you want to do, it sounds like mostly you would want to print on canvas and/or heavy watercolor paper, not something more like regular photo paper, is that correct? That is what is driving my thinking. If that's correct, then the quality of the underlying print may not be too important, and then the issue would be not mainly dye ink versus pigment ink, but how well dye-ink printers would feed and print on the types of media that you want to then draw and paint over. I am not sure of the P600, but some of the Epson models have an extra, straighter media feed path that works better with thicker / stiffer art papers and canvases. Even the second, straighter feed path on the Canon models involves significant bending, which affects feeding, and probably for that reason many of the Canon models have large minimum margins, 30mm each top and bottom, when you set the media type to something appropriate for a thick art paper or canvas (these large margins do not apply to regular photo papers). Maybe check out the Epson XP-15000, a dye-ink printer that Wex shows at £249, and see whether it might meet your needs. I don't know whether it has an extra, straighter feed path, but that would be a significant question.