Jebbo, I see (I think) what you trying to do or have happen rather, and no it does not work that way, if X number of bases are taken this plane sudenly becomes available, the tools we have to use are available to you offline, all the setings are their for you to tinker with, if you want to understand how it work's.
Karnak, is bang on if we get a Ki 84 it will free up many if not all of the restrictions presently being placed on the US plane set, it also would open up China as a CT set up area for a face off with P51's. The Japanese also nead Better late war atack aircraft, Juddy's, Jill's, Graces, Ki 102's ect...
Simply Put we nead more Japanese Planes.