option d is already normal, and is not OP. u r suggesting that an active player must be penalized. LOL.
You remember our game in the "arms race" event, we both and one other guy against more than twenty player coalition against us? Okay some of our enemies are gone inactive, but we won only by using our heavy air force.
When I look into the PL games or other games with a lot of veteran players, all of this guys use the most of they resources for the air force. If the time is come they all start the research for interceptors and bombers if the new level is available.
So I think it will be good to reduce the influence of active air control is better for this game. Active player can already control better all other units, react faster if some try to land on your coast. Control the production or start to build new units then the normal players. Why more?
Would you like to play with your friends in a game where gold is banned?
Watch for the next season starts in September!