I'm sure this already crossed someone's mind, but it sounds like the solarplate process is similar and could hold a solution. In it, one exposes the plate using a halftone screen and then exposes the plate to the image. Perhaps one could use a random-dot half tone (aquatint) screens to expose the photoresist plate, then remove the screen and expose the plate to the image (either through contact printing or through a camera). Depending on the nature of the photoresist plate, the half-tone prep could be done well in advance of the image exposure.