I have a generic ImageFile content type that uses MediaDescriptor for jpeg, gif, png, svg etc.

Now I have a requirement to restrict the type of file a particular content reference can take to only jpeg. (To stop people from using massive PNGs or BMPs for a certain property).

Is there any reason why I shouldn't just create a contenttype for each file type so that I can use the AllowedTypes attribute accordingly? So I'd have something like this:

  [ContentType(GUID = "someguid")]
  public class ImageFile: ImageData
  {
public virtual string Copyright { get; set; }
  }  

[ContentType(GUID = "anotherguid")]
  [MediaDescriptor(ExtensionString = "jpg,jpeg,jpe")]
  public class JpegFile: ImageFile
  {
  }

  [ContentType(GUID = "anotherguid")]
  [MediaDescriptor(ExtensionString = "png")]
  public class PngFile: ImageFile
  {


  }

  [ContentType(GUID = "anotherguid")]
  [MediaDescriptor(ExtensionString = "ico")]
  public class IcoFile: ImageFile
  {

  }

// then I can do this:
        [AllowedTypes(typeof(JpegFile))]
        public virtual ContentReference Photo{ get; set; }

I guess I'm wondering what effect that would have on existing images that were uploaded as an ImageFile originally.