I’d like a different plane model for each level
You don’t need this. The planes got outfitted or retired from service.
For example, when interceptor gear was invented, all planes got it. They didn’t let any planes in combat missions without the latest improvements, because pilots were of more value than the plane.
When metal aircraft frames were used, the advantage in ability immediately made the previous model incredibly obsolete. Meaning the older types didn’t fly and were replaced as new ones came on line. The process was quick like 2-3 months.
So a plane made in 1914 never flew in 1916, unless it had the latest developments.
This is not like WW2, when early war planes still flew for a few years, they did have overlap because the cost of these planes were much greater and more involved technology.
So you don’t need 14 types of fighters, just the one.
At the level of detail, the sculpts look the same for the most part. So you don’t need this.