Feitorias are an inherently imbalanced concept.
Not in terms of gameplay balance; more like balancing on the head of a pin. If you make them a fraction too cheap, they allow infinite resources and all they need to do is wait long enough, and victory becomes inevitable. A fraction too expensive, and they’re never worth building at all, since they take too long to repay their value and you’d be better off just having a normal economy.
No matter the cost or payouts of a Feitoria, the optimal number will either be 0 or 5.
I have an alternative way, and it’s roughly based on the Malay Fish Traps, which used to have infinite food. They were really fun with infinite food, but it too was inherently imbalanced, so eventually they were changed to have 3x the food instead. So, here’s the idea. It’s really pretty simple.
Feitorias draw from one shared pool of bonus resources.
Let me explain.
Now, in a typical game, the Portuguese player might build 5 feitorias and the game might last for 40 minutes, with 20 minutes of production. That translates to 2000 Food, 1200 Gold, 900 Wood, and 500 Stone, each, or a total of 10000 food, 6000 gold, 4500 wood, and 2500 stone.
Now, imagine the Portuguese player knows this is all they get. If they build one feitoria, they get it in 120 minutes; if they build 5, they get it in 20 minutes. If they build 10, they get it in 10 minutes. Build too few, and you don’t get it all before the game ends; build too many, and you use it all up immediately, and don’t have any military besides.
Suddenly, there’s an actual reasonable argument to be made on how many you should build! Should you go all-in on feitorias and extract all the resources immediately? Or should you just build one or two earlier on to get some extra resources, especially if you’re being pressured and are unable to fully focus your economy on what’s available? Maybe 3? 4? 0? It would depend entirely on the game.
This change would allow feitorias to be buffed in terms of extraction rate, up until they are nearly as strong as normal villagers, because the long-term effects aren’t such a concern. Right now, a feitoria produces about as much as 8 villagers, which certainly is not a very reasonable alternative to a normal economy in most cases. If they instead produced at around the rate of, say, 15 villagers, that would be completely overpowered and unstoppable in the lategame as it currently stands, but not if they would run out twice as fast.
Basically, to make them viable in the main body of the game, you just need to weaken their overpoweredness on long games, and this would solve exactly that.