Maybe an advanced settings tab or something like being able to enter the exact value below the slider. also being able to set the vertical FOV, setting a particular aspect ratio, being able to set more extreme values (being able to set it really low and then zooming really far out to imitate orthograophic view would be awesome), actualy just like an orthographic syle view. much less important could be things like depth of field and other effects although that might be out of scope.