A long time ago before I left, I had an idea to make lots of gold that is outside of the scope of the game's expectations.
It is very difficult and also risky, but the amount of gold you can make, is technically linear growth but is limitless and has no hard cap. (Unless the devs ends up adding one)
Forced Labor and Military Service creates gold based on 10X and 20X of each count of crew and cannons you own respectively.
A ship can still hold crew and cannons even if they are not in a fleet, and because they aren't in a fleet, they aren't limited by captain, admiral or merchant counts which cost increases exponentially.
The plan is simple, which was to build and buy sloops and only sloops, because they are turns to crew and cannon count efficient. By stocking up on a bunch of fleetless sloops, with their only use because that they hold crew and cannons, you can, at high numbers, potentially make tens and hundreds of millions per card, or even, billions in a day from multiple casts.
I am posting this because I will probably never work on getting to that point. And this is so people know this is something you can do, takes lots of effort and is super dumb and risky that some system change would specifically target this when the devs catches on.
PS: You can become a pirate to reduce the upkeep costs.
PSS: You can make a deal with other people on the agreement that you will pay them for them to cast on you too.
PSSS: Forced Labor and Military Service are uncommon cards but is plentiful.