I would tear down / break all the walls, Because think this way: imagine seeing the stairs from any part of the house is not a bad thing. You will win a great area, and incorporate it to transform the whole area. Make the utility room half or even1/3 smaller. I bet you don`t use your walls in your utility room, and so do not take any advantage of the walls. In your utility room, washing machine l ironing area, all these items have empty space at the walls after 80cm height (especially washing machine) . At the ironing space: your height is 1.80m and your ceiling height is 2.30m= 50cm for a near to ceiling closet, why not using them)? Visit your nearest store for observing how people use narrow areas to use all possible way, the options for taking profit of the walls. Imagine a caravan, they use all possible little place for placing something.

You can also tear down/ break the wal between the dinner and the living room. There are visual obstacles that give people impression of separation between two areas. They are architectural illusions. Use them. Take away the classical doors, replace them with sliding doors. Sliding doors will make you gain each time 1sq m, if you move 4 of them, it gives you space for a small laundry room, two powder rooms. Also about living room; think about how many people come to your house each month? How do they behave (just sit on a coach having a beer, sit on a chair with you at the kitchen have a coffee or tea? If there is each time one person coming and not a whole crowd of population, while bothering having tens of couch? Try these tactics, it will help you a lot. You don`t need to change the general architecture, it is way too much expensive and permits are really long and painful. Just making these interior change will change considerably your house.