My suggestion for improvement would be to keep the same turn length, but to at least double the production capacity of both sides, and to change the research costs - dramatically. If production is doubled, then research should be quadrupled, so that it stays effectively at least twice as expensive as it is now. Also, more stratification is needed in the production (or supply) costs as the scenario suffers from the same basic flaws that any scenario that relies on the stock masterfile does - overly effective air/artillery strength.
You are right, air is overlay dominant in this game. It could be at points, if the conditions were right for it, however that wasn't reliable. Part of the issue, I think is that there are no real weather effects for air. Especialy operating on this scale, there would be weeks when air was completely grounded....and others when it's ground strike capability was severely limited due to poor visibilty. Not sure how to model that.