One possibility would be to swap the living room and the dining room. Since the current living room is larger than the current dining room you could still keep some comfortable seating (couch and upholstered chairs?) against the front wall for a keeping room/dining concept. Then your new dining areas (kitchen and dining room) and living areas (living and drawing room) would have good flow between them, which would work well both for family and entertaining. You could also add some builtin bookshelves in the drawing room or new living room to create a library area to add another fun element to the living areas. These bookshelves could be against the long walls in the drawing room, around the window with a window seat in the living room (former dining room), or built to create some separation in the open area between the drawing room and living room/stair area. Your plan seems to show some sort of builtin there, but I'm not sure what it is.

A thick concrete wall can keep your house cool. Steel will make your house hot unless you insulated the walls well. Insulated walls don't work very well in a flood zone. When they get wet, you need to tear them apart. You will need concrete for the foundation most likely unless you are driving steel pylons. There is probably a combination of the two that will suit your needs best. It would be helpful to know what you want to achieve by using steel. There are advantages to both. Steel floors can be cantilevered further. It is easier to make bigger window openings. Floor and roof spans can be lighter and quicker to build with steel, but the roof will get hotter and therefore need good insulation and need to be well ventilated. These are just general assumptions of certain building practices so that you know what to ask people where you live. The practices and resources vary from place to place and building something for a specific purpose can change the benefits of one material or the other. My best guess is that you will probably want to use both.

I think a comfortable distance between the island and the counter is around 42". It seems that you have only 30" between your cook top and the counter. I might be a little too tight. The wall between the entrance and the kitchen could be 4' long instead of 6', you would then be able to move the island a foot which would give you more room between the cook top and the island. Could you switch the location of the toilet and vanity in your dad's bathroom so your enter facing a vanity instead of a toilet which is a lot nicer.

Tsilanko, I would always recommend professional installation where needed. But what I am doing here is suggesting that WHEN you are planning to build or renovate, to consider how your plans will affect you in 20 or 30 years time. Split levels are very hep when you are young. A kitchen 3 steps down at 30 is rarely a problem, but might be a hazard at 60, or, as Marjie1059 suggested, if you break a leg. ... All my parents' homes were terrible for old people. They were forced to move to a bungalow in extreme old sge because the location and design of their home was more suitable for an active young couple with a large family than for an elderly couple with stroke disabilities. I would not want to move again, so my present home has features built in that make ageing in place simpler. Mostly small changes, like grab rails, and lever handles on doors and faucets. A major disability suddenly suffered requires major changes if permanent. I did look at this because it came up in the discussion, but if you look at the heading, Planning for Disability, it means just that. Plan ahead so you don't have to make expensive changes later on. But thank you for your advice, yes, major changes are not in the DIY domain.