"200 Niki's produced and it isn't perked."
My guess would be because its the only version available, and its not that unbalancing vs other rides, like the CHOG.
The LA-7 does need a varient that was so rare. No 4 cannon Spit Vs, no 3 cannon LA-7s. Stick with varients that were at least reasonably common, this isnt "Crimson Skies".
...and im not "anti LA", its a great fighter, and absolutely should be in the game, has a very interesting history, many top aces flew it.