Wait what? So it's harder for the sake of being harder with no other gains?
I am all for extremely complex systems if you can do great things with them (like general architecture in DF, you can do 1x3 rooms or 5x6 rooms with ornate walls and furniture). But an extremely complex system just to obtain "game time"? (what food essentially comes down to). That's homework.
Make it complex if you can make it rewarding, if not, there is a limit on how complex you can get. Make it so you can have the reddest, biggest, tastiest tomatoes of the vicinity if you spend time, but don't over-complicate a simple timer/happiness mechanism such as food.
Still, what available crops are into the IF thread? There HAS to be some advantage to make up for the added complexity. Wood sources? Chemistry? Healing herbs? (realistic or fantastic style). Have you planned about modding so those advantages can be added at least? Plus, IF only seems to be "difficulty once" as in once you solve it, it's the same as now. Let me know, this is interesting.
Toady's little bullet point includes planting trees - both orchard trees for fruit (implicitly annoying to set up, and not as productive, but low maintainance after the first year or two and a reliable, low-labor source of food, if possibly taking high acreage relative to other crops to feed the same numbers), and for wood.
"Healing Herbs" can only exist when Toady makes them available by expanding the current symptoms mechanics, which is beyond the scope of Improved Farming, but something I would like to see, and farming is the obvious place to get them, especially as Improved Farming can make it possible for there to be growable herbs that are, thanks to high soil requirements and
Chemistry can only be as good as the number of products we can really make from chemistry. You can make plastics and paint and shoe polish from peanuts, but those things don't really have a place in DF right now. Maybe someday we'll get an Improved Materials Science thread, but the game's number of materials are rather rudimentary right now - pretty much everything is made of food, wood, stone, or metal. (Yeah, sure, there's a few extras, like gems and glass, but they're basically not terribly important.)
But for all that, the primary benefit still IS the complexity. The fact that it's a real system you do have to grapple with, and a real challenge to the survival of your fort, so that there actually is a challenge to your fort that doesn't come in the form of hostile creatures.
And yes, I've been doing my best to come up with ways to automate it so that it is a solved problem specifically because I don't like tedium, and I doubt too many others do, either. The challenge is supposed to come with the scaling of the complexity of the farms - that you can't simply set up a single farm system that will produce all your food needs forever, you need to build more elaborate systems as your fortress expands, especially in response to problems like water consumption (and aquaduct engineering to supply it), the rate of fertilizer use (especially underground, where mushrooms need some sort of biomass to feed growth, as they aren't photosynthetic, which means either cutting down increasing numbers of trees as fuel for farms, or finding some substitute biomass to add to those farms), and especially pests, which are increasingly attracted to your fields the more crops they hold, and which multiply rapidly when they gain access to a food source.