If I may say so myself, it is a very elegant way to represent the social development happening during the later Roman republic:
-People are pushed from their lands by latifunda (slaves, which take presidence in food production 'space')
-They move to cities
-They don't actually add anything to your country, but drain resources
- You can freely draft them into the army as you don't need them for food anymore.
But thats the problem. With just a flat output of food you dont get to represent this right? All freemen in the city will produce food. And what you will have is cities being major centres of production (as they will have more freemen than any territory), which is absolutely ridiculous and breaks the system even more than it is now.
Also, I dont like the suggestion because it leaves us much like we are now. Lots of food produced without the player doing nothing. Food production wont depend on how well you manage your pops, improve infrastructure etc, instead, the more pops you have the more food you will produce, which is again, very urealistic. And without having to do anything, which is the problem we are currently debating in this very thread. Food production should take a minimum of managment from the player if we are all agreed that was the most important economic factor. Why can we manage taxes or trade but not food? Building a few buildings doesnt mean micromanagement any more than the current system already does. Also, without going into a production and economy overhaul and assumng it remains the same, food tradegoods already produce food without having to build anything. So its not like the world would starve until you do it.
I would be willing to settle in a mixture of both proposals, where pops produce an amount barely enough (and not enough in many parts of the world to sustain itself) and you have to build those farm buildings to increase their food output maybe? Also the terrain type should be massively influential. A freeman in a farm in fertile egypt should produce a lot more than a farmer in a hilly territory Greece.