That's fine, I'm open to anything that will improve the game, all I did was to present what I have done for myself and my head to head opponent, and for us it has worked quite well, and I believe it's because we play with the 40 unit armies, if we were to try it with the standard 20 unit armies The AI would be spamming stacks.
The way the AI handles spending is what I believe is hampering their ability to compete with the player, I've had nobody tell me this, it's just what I figured out for myself, it's all based on a % that is set by CA/modder, if the modder sets the BASIC_SPENDING_BIAS_RECRUITMENT_ARMY to 0.4, then 40% of the income is allocated to recruitment, and perhaps 30% to building, and 10% agents, 10% navy and 10% diplomacy.
So if the AI is making 2000 per turn, then 800 is allocated to units, 600 to building, 200 to each Agents, navy and diplomacy, and if they cannot afford the chosen purchase, they save the money for the next turn.
As you can see your not going to get much for that, and once they have an army of noobs, their economy will pretty much stagnate from upkeep costs, and this is why I believe that the mid game AI still has low tier units and buildings, making the mid to late game easier and boring, and cutting the players income will not change this behavior at all.
P.S the above is purely conjecture, if it's not how it works please enlighten me, it could be that the 0.4/40% is the chance to recruit units