Would it be possible to make this as a firefox addon? It'd be awesome to have this available here, but would be even better if you could use this on any website.
Well, a GIF extension would be much better, but would be specific to Firefox. What you can do is grab the first bookmarklet at
the bottom of this page.
It will embed FrameViewer on ANY site, and it'll work through ALL GIF files. This can be really annoying sometimes, because each little GIF icon will end up having the toolbar. This is also rather buggy as it is, because a lot of special positioning in GIF files are not properly handled yet (still working on an universal method for it). In fact, some images will just disappear for some reason. The tool was made for plain inline images, so it works best with those.
The second bookmarklet there will open all GIF files in the viewer page, which will avoid all these problems. I also followed Gil's suggestion, so if you're coming from this site, it'll only grab the zoomable images.