So I got my plan from the architect. As expected, they removed one of the three "bedrooms" to make a living room in an open floor plan connecting it to the dining room and kitchen. Dumb. I have by default three bedrooms, and I intend to keep them, and use one as a desk/reading-space/living room type of place: a desk, some comfortable couch and/or chair(s), a console for a TV, some speakers, some book shelf. Also, by making everything so open, it creates a LOT of useless navigation space, such as from the kitchen to the entry hall (why??). This is a symptom of house-flipping where people buy apartments without much space and take down every wall they can so everything can be shown in listing photos, with more light. It looks "nice", but it's killing the usefulness of the space and the next thing you know you need three bathrooms and a walk-in closet and a powder room and mess kitchen and what not because no room is functional on its own anymore.
Formal vs. functional: Formal living rooms fall from favor, but get creative replacements
Open floor plans often cause living rooms to be missing a wall; either you have no proper wall for the TV, or the couches are misaligned to the TV because they can't stand against a missing wall. It makes the living rooms useless, a room people essentially never really use properly or at all. Plus, because the kitchen is being used and loud you raise the volume of the TV and now everyone speaks loudly to each other and the neighbors have to raise the volume of their TV or music to stop hearing you.
I have seen how my landlords with their two kids used their home for the past decade, as the kids grew up from toddlers to teenagers, I learned so much about how to use space from that. When they have guests, they are in the kitchen/dining room or on the patio, NEVER in the living room. The kids go outside to play in the backyard or the backstreet or just leave the house, otherwise they go in their own bedrooms. The living room is only used to watch TV, only by the parents, only at night, when one has down time while the other is doing something like the laundry or preping meals for the week or whatever, barely ever. The kids use their mobiles. And if both parents are using the living room, which essentially never happens, chances are one of them is looking at their tablet.
So my plan is to make the dining room and kitchen open to each other, with the dining room close to the exterior to get a lot of light, and make it an almost living-room-like space. There's a table, so you can sit at it comfortably even if it's not to eat, there's a couch-like seat with a big drawer underneath to put the vacuum cleaner and mop in. More often than not the table is unused so kids can use it to do whatever, be it play games, draw, whatever, and be sent to their room or out if needed. You can easily add a TV on a wall if really needed, and it can be used like a radio to play some music in this room where people spend more time than the usual living room. The space being open to the kitchen makes both more social, and whoever is in the kitchen is not excluded from the people in the dining room. I can imagine the kids doing homeworks or playing in the dining room or at the kitchen counter while a parent is preparing meals and talking to them or whatever. At the same time, both rooms, considering how they are used (to cook, eat, and spend an evening with guests), can be loud, so it's another good reason to put them together but separate from the other rooms.
Also, the architect put the toilet in the bathroom, and I'm trying to convince them to separate it. I don't want a prison bathroom. Instead of having two vanities in the bathroom, I want a single one, a shower, a bath tub, some storage. Another small room with the toilet has its own smaller vanity and a bit of storage. That way, I still have two vanities, and both can be used at the same time but each in their respective space (I really think that two persons using two vanities next to each other is conflict-inducing, even if just in our heads). And this way, if anyone needs to use the toilet, the bathroom with its tub, shower and its vanity is still accessible, and the likelihood that someone needs to use the toilet while both vanities are being used is very low, and if they had all been in the same bathroom the mere use of the toilet or shower or bath would have caused the room to be hijacked. Imagine your teenage daughter hijacking the bathroom for 30min+ and having no alternative but to kick her out or wait for her. Next thing you know you are removing space from other rooms to make a whole second bathroom anyway.
If a mezzanine is ever built, I would move the toilet room upstairs and expand it just to add a second shower. We would only have one toilet in the house, which is I think fine; it's usually not the toilet that needs to be used at the same time, it's the vanity or the showers.