Thinking about it, the fat spine needn't be of concern if done right. The late Spits were nose-heavy so some added weight aft of the cofg might be beneficial. A bulge aft of the wing wouldn't necessarily add meaningfully to the drag and might actually reduce it and also lead to the early discovery of the area rule! A revised (taller) tail is hardly an insurmountable hurdle. Incidentally, I meant MiG-21SMT as in position not in degree, I'm not talking a huge bulge here. The more I think about it, the more I like it. The end result would even still look like a Spitfire! How many Spitfires do I have....
As for your pronouncements, jcf? I guess I disagree with pretty much all of them. [Shrug]