Of course that would be nice, but there are two things that make your idea difficult to realize:
1) Levels and models are often not compatible for different games. Each game has its own needs and enviroment. As for model-formats: There are so many formats, it is not surprising that many of them might not be irrlicht-ready. But you can use a converter or a 3d programm which is able to convert the meshes (e.g. Blender3D is able to handle many formats).
2) Most 3D artists do not share their work for free. And those who do often do not take requests for certain models, they publish models they worked on because they wanted.
Sorry, that might not sound very optimistic, but it is what I experienced. And if you really want to realize your idea, you should do the first step: Create a web presence, collect models ask 3d modellers to join, etc. If all is going well, I think it has a chance to become a part of the official irrlicht page.