The problem I have saving out with PIL is that if there's no transform but you save the file then the duration is set to the first frame duration for all frames (I will look to flag this against the project). Manually building the GIF was very slow and produced a huge file.
I looked at wand as an alternative but the time required to just save an animated GIF out with wand was prohibited.
So instead if the original image uploaded is an animated GIF then any variation generated, no matter the filters applied, will return a copy of the originally uploaded file.