If you're so desperate to get fisheye from Corona, then you should know that there already exists some workaround. You just need to render from camera with spherical projection, load that image into any app that is capable to perform projection transformations (ptgui, hugin and many others) and transform from equirectangular to fisheye. It's not very convenient, it requires more resources to render, but at least it works. And it also has a nice bonus - you only have to set up position of the camera in 3d app, but you are free to choose any rotation that you want in post.
Having said that, here's my +1 for fisheye projection in Corona :]