So I've seen quite a few threads proposing ways to make feeding a large fort more challenging. Most of these consist of making farming harder, more complicated or just increasing the rate dwarves eat. However, I think there's a way to increase the challenge of sustaining a fort without making the learning curve harder for new players; food preservation!
The idea behind this is that in DF, once food has been gathered (and sometimes cooked) it functionally never rots in the stockpile. This isn't to say it never rots, just that it rots so slowly that while you're playing the game it never actually is noticeable. Also, prepared meals stay fresh forever, mysteriously.
I propose raising the rate the food rots in a stockpile. Food, including prepared meals, should only last around 1.5 seasons (to allow for mods where there's a winter season without crops) before it starts to rot and is reclassified refuse. It should also rot faster on warmer maps. To get around this, players can craft a preservative; salt (Inspired by
this thread). Salt can be ground at a mill or quern from rock salt, imported in bags from caravans, or gathered from the sea using a tool in a new gathering zone. Jobs are automatically queued up in the kitchen to salt edible, non-prepared meal items. Salted foods will rot slower, and meals that contain them will also rot proportionately slower (plus have higher value - however, this actually makes sense; a caravan would pay more for food that would stay edible on their journey). Food bought from caravans should be pre-salted.
Secondly, vermin should become more of an actual threat to your fortress. It's calculated that today, about 1/10th of human produce is consumed by mice or other animals before it reaches our plates. This was probably worse in ancient times, before pesticides and systematic rat poisoning. Essentially, the game should keep track of how many edible items there are on the map (it already does this so that you can have stocks). As your stocks get fuller, the rate vermin naturally migrate onto the map should increase proportionately to model them breeding more rapidly thanks to greater available food. This causes players to have to redesign their forts; food and seed stockpiles now need to be surrounded by animal traps if you want to remain efficient, and a sizable cat population is much more important than it currently is.
Now, this makes things considerably harder, but only adds challenge as your fort grows larger; early-game forts should be fine by virtue of not attracting large swarms of vermin. It also adds a new, optional industry (salt), adds incentive to trade, and allows for players to combat the added difficulty through design strategies. Based on this, I think it's a reasonable addition to the game; it adds difficulty and complexity, but makes the learning curve less comparatively steep (the game gets harder as you go on as opposed to easier) and is something players will quickly learn to adapt to.