I have recently had the idea of making a tool for Pokérole. One of the components would be possibly generating encounters. I could try going the way of the Walls Svg importer script and parse what the user pasted, but this may include images that that would be a nightmare to put into a text box. I propose that scripts be able to install "File handlers". When an unknown file is encountered, Roll20 goes through the list of registered file handlers, feeding them the first N bytes of the file (or for an XML file, maybe the starting element of the root), and then passes the file stream to the one that claims the file (possibly throwing a fit if two handlers claim the same file). Then the script reads the file as it comes in and does its stuff while reading the file. It should probably have a mechanism for adding images to the user's library since that may be part of the input.
