I feel a bit like this is repetitive of what others have said, but this game suffers from wicked inequality, and imo no market mechanism to give small/new players a chance to broker deals with older/larger players to catch up. Sure there are tech deals, but that's small potatoes.
Why have an aid cap? Also, where is the system of international loans and interest? It would be neat if there was a marketplace for cash, where rich nations could offer large amounts of cash (say, $100million), and state an interest rate and compound period etc.
This could be developed organically just by raising the foreign caps (and allowing an unlimited # of foreign aid slots). If these changes were made, the game play would effectively still be the same, but there would be a new dynamic where large nations actually took some real risk with their cash (to earn money and help allies in large numbers), and simultaneously smaller nations would have a legitimate chance of catching up.
I suppose this increases the risk of certain nations just giving all their cash/tech to a friend before quitting the game. But honestly, who cares?
I also think it would be neat to change the cap on war slots to be determined by NS instead of by a fixed number of wars. So something like "any nation can declare on any other provided the attacked nation will have less than 2.5x NS in attackers following the dow" . So that way one 25k ns nation could declare on a 10kns nation, but no one else. Or, 2 10k NS nation could declare on the 10k ns defender. Or, 10 2.5k ns nations could declare on the defending 10k ns nation.
I think that change would be more serious for changing gameplay, but it would go a long way to equalizing play, I think.