The C wing was specific to the Spitfire V which had the A, B and C wings. The C was also known as the Universal wing and was used on the Spit VII, VIII, IX, XII and XIV. It was not designated the C wing on them however. Later the E wing was developed and used on the IX, XVI XIV and did receive the letter designation.
The Spitfire IX we have in AH has the Universal wing already.
As for the Spit XII, I'm all for it as it's my long time history passion. That being said, there are many other birds that should come first to fill out the plane set before that.
As for a clipped XIV. They really didn't show up until postwar. The wartime XIVs had full span wings as they were interceptor/fighters. It was when the jets took over postwar and the XIV got relegated to the ground attack role, that the clipped XIVs were more prevalent.