After re-reading the DNSL I'm not sure this falls under anything there. But it is a request to fundamentally change the game, in that it adds a brand-new resource. That would change everything. You would need brand-new buildings in each Age to produce Food, and/or you'd have to convert some of the existing buildings away from Supplies and/or Coins. Since everyone will be producing fewer of those two things because we'll need to carve out space to produce Food, that leads to rebalancing everything else in the game: normal buildings; Event buildings; Quests; Event tasks; Campaign Map costs; GB production (does the Chateau boost Food rewards? Do you change an existing GB to boost Food like some boost Supplies and Coins, or introduce a new one?). Does Food increase Happiness or is it a brand-new metric? If it adds to Happiness then all of those buildings and GBs and tasks will need reworked. If its' a new metric, does it affect other things like Happiness does, such as production and military bonuses? I'm sure I'm forgetting a hundred other things.
-1 to fundamentally rehauling overhauling the entire game.