Keeping in mind that it doesn't matter what kind of material is used, or which type of powerplant is installed, as long as it is full scale.
I, for one, would like to see an Hs-129 on the airshow circuit. And I always thought it would be neat to have a flyable Ohka 11 (Baka Bomb) as a high speed rocket glider. There are solid propellant rockets with at least 10,000 pounds of thrust available, so it wouldn't be hard to build one that could launch off a runway, or fit a B-25 with a special rack to launch it in the air.

Something else I'd like to see is a PT-13/17 modified to look like a Gloster Gladiator. The actual measurements of both aircraft are nearly the same, so it wouldn't be much of a problem modifying a PT airframe into a Stearman Gladiator. I know there are other things that would need to be changed, such as the tail feathers, but that's not much of a problem either. It wouldn't have to be exact in every detail, but it would sure look a lot better then just another stupid PT.

So, any other examples?