I have a suggestion for improving the balance
I think that the balance should be based on the core nations, that is, the Russian Federation and the USA, you can simply make the US and Russian equipment historically correct starting from rank 5, and then adjust the other nations based on these two,
since in fact all the main equipment in the game is the equipment of these two countries, be it MiGs or the F series, which literally everyone has, this will help make the balance system more transparent and simpler
and then, based on the win rate of the equipment of secondary countries, change their BR to adjust it to the balance of the core nations