I. too, have always had a soft spot for the mockingbird. I own one US BCR mockingbird and one sort-of partscaster one I made from a generic Samick or Cortek body and another generic neck.
The body style has some flaws, like neck dive and the fact that it doesn't like to sit in a lot of stands. I'd love to see someone make a reverse mockingbird (left handed body with right handed routes or vice-versa), which, I think, would still look nifty and solve some of the neck dive issue (assuming the strap button is located on the tip of the horn). I'd also love to see one with a beveled cross-section, to cut down a little on weight (which could make the neck dive issue worse). But sadly, I don't think that there is really a good market for them, especially heavily modified shapes based on the mockingbird.