give us the XII!
Why? Fly the Spit16, and it outperforms the XII.
The thing is, the XII, outside of those who absolutely love the detailed history of the plane, isn't useful. Nor is it better than anything we already have in-game.
What makes it interesting is that it was around in early 1942. At THAT TIME it was very fast. Much like the Mossie was fast against early 1943 models but in the MAs it's pretty much an easy target, you'd get the same issues here.
To quote an article on the XII that lists speeds:
"The resulting aircraft was very fast at low levels, reaching a speed of 372 mph at 5,700 feet and 397 mph at 18,000 ft. It was faster than the Mk IX up to about 20,000 feet, but above that height it was slower."
Well, let's look at our Spit9 and clipped wing Spit16:

So, our Spit16 is as fast at 5000ft, even faster at 20,000ft, and stays fast up to almost 25k.
I know, I know... The die hard fans want it, and I can't blame them 1 iota. However, if you wanted to you could just fly a Spit16 and pretend, and get comparable results.