I'm Dutch too, not sure if it would be something for a full expansion since I'd really expect a lot of content there but maybe a game pack with a world that adds more than like 4 lots. It could have two regions with several lots: An Amsterdam style city region with a few classic Amsterdam style houses as well as a cafe to visit and there could be an open market in the street now and then where you can buy various stuff and there could be some street performers.
The second region could be outside of the city with more of a farm theme, with windmills and tulip fields around. It could be a very pretty and colourful place. There could be a miller NPC to interact with, to buy grain from to bake your own bread.
Cheese making could be a new thing you could do in this pack, a new skill with new objects, along with a cold storage to put your cheeses and let them ripen. If you have cottage living you could use dairy from your cows for it, but here you can buy that from a farmer too. It should have something special you could do with it at a high level though, like making some special cheeses with unique effects. One could have a disgusting smell and cause sims who eat it to also spread that smell until they do something to get rid of that. Another cheese could be deadly if eaten, and be for display purposes only, increasing in value over time. Yet another could be addictive, eat it and your sim will want to eat all the cheese on the lot until that moodlet expires, getting sad if there's no cheese to eat or you won't let them eat it. It could also be possible to construct some things out of cheese.
Clogs could also be created at the woodworking table as a new option, an alternative woodworking table could be added too since there's still only one since the base game. It would unlock the option in CAS to wear wooden clogs in various designs.
Fierljeppen could also be done in the farm area: Using a long pole to vault over a waterway. Would require a high enough athletic skill, otherwise your sim falls in the water. It could be a short cut on one place to get around faster, and elsewhere with a longer more difficult jump it could lead to a hidden little swamp area. Could be a swamp monster there during certain hours at night that your sims could try to avoid. It could spread a nasty sickness to them that could be deadly if not cured, but this area could also have some interesting ingredients only found there. Like the cure for that disease and something to make one of the rarest cheeses.
Stingy could be a new trait introduced, sims who hate wasting money or hate wasting anything really. They prefer cheap furniture and items, will never tip and could have a lot to say about other sims being wasteful with money. Are very happy with anything free though, but purchasing any expensive item could give them a negative moodlet. And it would stack so the more you spend, the worse it gets and the longer it lasts. When out on a date or on other outings with other sims, they can suggest going Dutch, each paying for themselves. The stingy sim is no mooch.
Complainer could be another new trait, also very fitting for our culture. (also we seriously need more negative traits.) The complainer is not mean or sad, but they certainly have strong feelings about, well, anything. They need to vent, online, in person, on social media. Other complainer sims could enjoy that exchange. Whenever something bad happens to them, they will not let it go, their negative moodlets last longer but that time does get reduced when they get to vent about it. Watching news could also get them really riled up, they would get angry just from watching that. On the plus side, they are very open to listening to other sims vent or complain. To them that's welcome communication. It helps them build up relationships faster.
Nonchalant could be a less negative new trait though that also fits us Dutch. These sims react with a shrug to whatever weird thing happens around them and just go about their business. Like they have seen it all already. They would way more often be in the neutral 'fine' emotional state, they could require like 3 points in any emotion before it kicks in for them, so would also not so easily switch moods. Some other sims might find them uncaring though, so some interactions might be more likely to go poorly when directed at these sims. Like propose to them and they'll still act casual, like it's just another tuesday.
Soccer could also be brought back through this pack, Sims could play soccer, it could be added as a new career. Would just require athletic skill and nothing new there, but Sims can now also play soccer when outside. Watching a soccer match could also be a whole thing, maybe a new kind of party to host for Sims with friends. Athletic and Bro sims could really go nuts with that.
