So this is for the future, given that we will have a reset. But what I was thinking is the balance of new and old players.
Inevitably you get to a point after enough time passed, when the gap between them is simply too big, first, you won't be able to catch them -ever-
Secondly their contribution let that be economic or military is inferior in comparison.
To circumvent that, new players could get a boost in these areas, raising their stats to a level say one year behind. For example, if you can get say 100 strength points in one year maximum, then after two years passed when the top players will have 200 strength, the new ones will get a boost to 100.
The boosts could be sold for real money in the store, I'd keep it's price low, so people are actually willing to spend on it.
In special events you could give these boosts for free -temporary-.