Agribusiness is a terrible building. But I think its main issue is that its trying to push food at a time when food has lost nigh all of its value. Growth is just not needed at this point in the game. So I would approach it in one of two ways: 1) Instant Bonus: Similar to the new medical lab idea, give it an immediate one time bonus when its built. This is not my favorite idea, but its an option. 2) Hospital-esque Bonus: My favorite idea is to use the hospital concept, and put back the "business" into the building. Have the city gain +X% of your food in gold. Similar to how faith is retooled into GP late in the game, food has to be retooled to stay relevant. More food is simply not the answer. With this concept, now food = some science and gold in the late game. That gives it some value.