This is logical but you can see the amount of games played as axis / allies by top 200 players in the charts and whilst less its about 6000 axis compared to 4500 allies so the imbalance isn't that great. I'm not smart enough to crunch the numbers but a 25% difference in games played probably cannot fully account for the difference in win rate. Also consider another chart (I cant recall where it was) showing the win-rate curve across the entire playerbase which showed a steady but shallow rise until the top 50 where it rose exponentially - the allied teams being played by top 200 will have a broader range of skill than axis opponents but not necessarily by that much. I don't agree with the OP suggestions - but I do think as games get bigger axis gain a large advantage. I think to pull big games back towards a balanced center line needs a different approach - looking at resources and synergy between OH and OKW
I am not sure about where you got the 4500 vs 6000 games; but this chart shows ~2500 axis vs ~800 allied top games. That means that at the very least, 1700 of those top 200 axis games were against allied teams that were not in the top 200. This would explain the win-rates reasonably well.