I see what a beast the script filter would be now from reading on Caja and the content filtering already in Freenet, I don't think this is a good idea for a first contribution.
I'm interested in the progress bars idea, it would be nice to see what's happening when a freesite takes ages to load, especially to people trying out Freenet for the first time. Could implement a progress toadlet at 127.0.0.1:8888/progress/<key>... which could preload the file into FProxy whilst updating the status to the browser.
