I think the very basic of survival aspects of being a dwarf (food, drink, shelter) should be as simple as possible, at least initially.
You plant a seed, it grows, you harvest it and turn it into food & drink.
Now, some things need to be addressed:
Seed roasts made of seeds, seeds, and more seeds. Prepared meals need to have something of substance in them. A plant or meat or bread? needs to be the core component. No more seed/wine/seed/syrup dishes.
Perhaps breakdown food into these parts:
Core: Meat, fish, or plants.
Sauce: alcohol & other drinks
Season: extracts (syrup, sugar, etc.)
Garnish: seeds
So a simple meal is just a core + sauce, a medium meal is core + sauce + season, and a lavish meal is all 4 components.
Anyway...way off topic there.
The basics and what supports those basics needs to be as simple as possible. It's one thing to have Fun because you accidentally tapped a aquifer and the pressure shot your dwarves off a cliff. It's another thing to have Fun because your marksmen weren't nearly as effective against that giant skeletal whale as you thought they would.
It's another thing to have Fun because you can't figure out how the hell you're supposed to get food & drink to your dwarves. That isn't fun, Fun, or even FUN!!!!. It just sucks.
The key for making dwarf fort accessible is to make the very basics as simple as possible. Most of us who've been palying for awhile can make a functional fort in our sleep. It's the advanced stuff that is far challenging and fun (Fun). Magma work, water work, mega-projects, challenges, seige warfare etc. That stuff should be as complicated and challenging as possible. It will always be Fun as long as the basics are straightforward and simple before going convaluted & complicated.
As for irrigation: It rains (if you have weather turned on. If off, it's assumed it rains anyway
). In caves, moisture drips from the ceiling. Realism concerns done.
Now, I do agree that it should be harder to feed larger forts then it is. Perhaps reducing the number of outputs from a field by a fair amount. As is, it's very easy to break even...perhaps it shouldn't. You can (somehwat) always gather palnts/f for drink and fish/hunt for food. Perhaps farms should be easy to set up but hard to manage.
Or perhaps they should require more work to be successful. As is, you plant the seeds and leave for a season, coming back to harvest. Perhaps there should be irrigation tasks (just once per farm plot or maybe per 3x3 square), or 1-2 per season the farmer has to weed. The longer the weeds are in the farm plot, the lower the crop quantity will be.
The dwarves can take care of it themsevles, but a bit more managing might be required to make sure your dwarf isn't busy doing something else when he should be tending the fields...