the Ki-43 isn't the most historical thing we're missing in AH: that would likely be the Panzer III at the moment.
The Ki-43 does not fill the biggest/worst gap in special events, various bombers, and some EW fighters do that.
The Ki-43 is not the best figher we could add based on impact/use in the MA. Most other potential fighters would do more.
Adding the Ki-43 would not make us any more worthy of a 'well done' than adding anything else would, as we've already earned it. AH is the best WWII-era combat sim out there, has one of the best GV aspects, and on top of that, AH is actually run out of passion for simming. I'm sure Hitech isn't wanting for cash.
@ Karnak, essentially every fighter we have with a low wing loading and large wing area looses its ability to turn at higher speeds. IIRC, the Ki-43 lacks hydrolic control surfaces, like the A6M. It was also notoriously fragile.
Based on this, we can safely assume that the Ki-43 will at the very least suffer a significant degredation of turning preformance at higher speeds, if not the near total lack of effectivness that the A6M has. Or possibly, you'll just snap off the wings if you try and turn too tight at high G's.
And it depends on what you call last-ditch. If you mean already capped and vulched, then yeah, the Ki-43 would hold a small advantage over the K4. But even with that advantages, its odds of doing anything effective are essentially nil.
If you're talking "Oh ****! look at the size of that darbar, we only have like 2 mins!" then the K4 is far superior. In 2 mins, I could get almost to 6-8k with a K4. And depending on the situation, that ranges from sufficient all the way up to too high.