Finally had some time to load up that save. In short..
It is 2000 ducats going into Sevilla, producing 4500 trade income. Not sure where the nearly 9k listed at the start comes from.
A few key jumps are done by the AI, but heavily persuaded by the Spanish Fleet tradepower.
You say you needed to lose mercantilism for the Indian trade-buff. You never took the Importation act which would have made you lose that, plus given you higher trade income.
Force limits are not even that bad, opposed to what has been said in thread. It is 544 force-limit (due to owning majority of the world) and 1654 ships. Your upkeep is 1 ducat per ship, which is double the normal upkeep (0.5)
Only 1200 or so of the ships were Frigates. Even deleting all the frigates at nodes with no traders, and reducing his overall naval force limit to 620, there is still a nice healthy profit being made. Though the trade income is a more modest 340.
Not when trade-based economy beats a tax/production-based economy with the factor of 1000.
This is what this thread is about.
More like a factor of ten. But it does require you to shift the trade from around the world. You have to remember that trade is also very lucrative compared to production which came via the industrial revolution which is after the Eu4 time period, and more the Vicky one.
After actually getting to look through the save myself, it isn't that broken. All it needs is naval force limits be more heavy, so instead of 'double cost' for simply being over, it should be 400% the cost for being twice times over the limit, then 900% for being 3 times over the limit (like colonies).
which shows that what this is is an obvious AI issue - the AI not being good enough at competing at playing the trading game - not a balance issue.
And AI issues are best addressed by improving the AI, not by getting rid of mechanics that AI isn't good at. The latter is occasionally the only way out, but the former is absolutely preferable.
It is actually a force-limits issue, not an AI issue. The AI generally sticks to force limits whilst in this case, the player went 4 times his forcelimits to pull off the stunt.
What I am going to do is set up a Netherlands game, then simply take 1 province at every node, then just spam them with Frigates. Should be able to reproduce the same results without a virtual world conquest.