Pretty cool, a subversion of the double exposure mode that (I think) Pentax has. Couldn't intravalometer do the same thing, you just stack images in post as an add function?
ML doesn't do any post processing in camera between images, but the camera does some digic magic for vignetting and CA fixes on each image. And I guess it does dark subtraction on long exposures too, could that be subverted to a different function for adding frames instead of subtracting noise?