I'd love to see a farm with farm animals (pigs, cows, hens, horses) and different kinds of grain. But also other types of "farms" could be possible: vineyards (or maybe as a GP?).
A tractor as a new gameplay objects that helps you to harvest your fields.
Other new gameplay objects could be: canning station, butter churn, smokehouse, chicken coop.
A lot of new recipies could come with the EP, too. E.g. sandwiches with different jams, new muffin and cake recipes that include butter, scrambled eggs, fried egg with spinach; new meat recipes e.g. tournedos, chicken breast fillet, and so on. That would be a great addition for home cooking and everyone owning "Dine Out".
New traits:
Loves countryside - This Sim loves to be surrunded by corps and farm animals. They love to work at a farm and get tense having a rabbit hole job. They can also use tractor, canning station, butter churn, smokehouse and chicken coop (wine press) twice as effective as other Sims.
Hates countryside - This Sim loves the city or at least a town, but the countryside is not a great place for them. This Sims gets a sad moddlet near farm animals and grain. They also get a tense moodlet riding a tractor. This Sim is very slow when harvesting or doing other farm related activities.
New aspiration: Super farmer - This Sim wants to be the best farmer in town. Harvest 100 grain of perfect quality, make 50 butters of good quality, make 50 cans of good quality, have 50 eggs of good quality.
Bonus trait: Farm Hand - Eggs will never spoil in your inventory, you can use the tractor, canning station, butter churn, smokehouse and chicken coop with triple efficency.
New lot type:
Farmer's market - Your famer Sim can sell the products from his/her farm here. The primary products like milk, eggs, meat, grain, vegetables, fruit will give them less money than the secondary products like butter, jam, sausages.