You could mount a TV which can swing out from the entry wall from the main house, or on the one opposite one near the back sliding doors, or on the floor, in the corner. Depending if you need storage on the back wall, you could have your lounge at the back of the room, or have a walkway between the back wall and the lounge. An easy moving lounge is great for moving into different positions around the room. I like the idea of the bar as a drinks trolley. Actually furniture on wheels is great for rearranging whenever you like. I usually have wheels mounted to furniture as I live on my own and it just makes it so much easier. Another idea, is a buffet across the wall of the three windows and a tele positioned placed above or on where the brick wall is in the middle of the three windows, and the buffet can act as a bar and whatever else.

Your mockup scheme is similar to our master bathroom we just completed - photo below. I know you mentioned storage being a concern - our mirrored cabinet has offered an amazing amount of storage in a very small space and also helps bounce light around. I was worried about black taps etc too so we kept chrome fixtures but added in a matte black candle and black potted orchid to create a similar effect which we can change out later on. Our floor tiles are dark but because they are semi-polished they actually bounce around a lot of light and don't make the room feel dark if that is a concern. We also have a huge fiddle leaf fig in the corner (not pictured) which adds a really nice feel to the space - a plant like that could help bring in the outside greenery in your bathroom. Instead of the storage tower you have to the left of the vanity could you do say some floating wood shelving, possibly with baskets added for more hidden storage? You could also bring in the 60s theme with what you displayed on there eg. photos as you mentioned? In regards to the window - a previous house we lived in had a window at about shoulder height in the shower - as well as letting in heaps of light it was amazing for storing toiletries etc!

Face it - gravity sucks. Your house was designed to be supported by the "poles" or are they stumps? You will need to carefully assess the value in removing them all. First you will need to engage a structural engineer to advise you, and he may suggest long steel beams that run across from one side of the house to the opposite side allowing the supports to be removed. However the financial cost in installing these long beams (and additional structure to support the beam ends) will be significant - there is no cheap fix. Once you have paid tens of thousands of dollars (maybe more depending on the length of the spans and ease of access under your house for installing them) you will have a large, open, low-ceilinged space with the proportions and feel of a shopping centre carpark. The structural engineer will need deep steel beams depending on the span between the walls, and this will reduce the clearance under the beams to much less than your current 2.1 metres. Save your money and engage a clever designer to find a clever solution that works with keeping the supports, and you will get much better value for your spend. Best of luck with your considerations, Dr Retro of Dr Retro House Calls

everything you've suggested sounds ideal and you will only need to build a frame underneath the stairs to create a wall to the side of the steps and directly under the top step to allow for a door and cover with the same wall lining and either add an electric or battery operated light under the stairs and shelving to suit what you want to store