Don't know how many have heard about it yet, but
here is the Inter Quake Model Format. From what I see it would be quite a good idea to add it to Irrlicht Engine, most of all since it has a well maintained exporter for Blender that works, unlike many other animated model formats irrlicht uses. Also it is rather tiny, yet feature packed and seems to be quite the preferred format in the Quake and modding community.
EDIT: So far already achieved a 10x reduction in file size compared to DirectX format storing the same file data.
Going ahead already to see what I can come up with
![Wink ;)](./images/smilies/icon_wink.gif)