Couple of observations Lots of mosaic tiles have sharp edges so you need to be very detailed in how you do this. Have you considered a corner (spayed front) shower bath combo. There are several manufacturers that make these in fibreglass and acrylic materials (some with spa jets also). That way you can consider a shower screen that would be integral.

I will start with an admission - I have read nothing of the comments. However I have helped a friend design a compact laundry. Here was how we did it. 1. Start with a list of everything - and I mean everything, include pegs, those little lint ball things for the washing machine, buckets, mops, vacuum, airers etc - that you want to store in the space. 2. Break that list into where you want to store it - drawers, wall, or cupboard - and then rewrite the list as cupboard, drawers, wall etc.As you are doing this, see if you can store those items elsewhere - we added a ceiling airer in the bathroom using pulleys. Also mark any item that a special storage gadget might help. We added to the back of one door (I think they were custom made 925mm and 2300mm high) a hanger for the vacuum hose, and in the cupboard a hanger that slides out for the brooms and mop. 3. Go measure the space you have, and be exact - if the measurement is 1457mm it is 1457mm. Also, see where you might "borrow" space from. We managed to add another 650mm deep, 750mm wide cupboard by swapping the two bedrooms around, and using space in the guest bedroom wardrobe. 4. Draw up a plan, and be really specific. If you think you need four drawers and a top mounted sink then plan that way. Whilst you are planning think over whether you want top spec and not hide it, or to hide it behind really nice doors. We used reasonable quality from Bunnings and modified because it was behind doors. Also, don't be afraid to "borrow" something from a different zone. In my laundry I used a round kitchen sink, because I didn't want a really deep laundry tub so I could use the room underneath. 5. Go and find a really good quality cupboard manufacturer or builder and ask them to look over your plan and ideas. They may tweak to assist, but remember you know your space and what you will be using it for better than anyone. In my friends case, she had a brother who assisted and made a super looking set of doors. As to resale value, that depends on who you want to buy it, but I have one piece of advice - don't go for the resale value, do it because that is what you want. In my friends case she turned her laundry into the bathroom, and then turned the oversized bathroom into a very natty study. Good Luck.

I feel the bedroom would be claustrophobic however. By my calculations, there would be only around 900mm between the foot of the bed and the wall - which is fine if it's a secondary space - but this is to be the parents retreat and it needs to feel luxurious and open. Di Njsd also indicated originally that the window was to become a door to allow egress to the patio outside. A bed up against that wall nullifies that objective.

In answer to your original questions: Install a normal centred shower drain. The long drains are a chore to clean, and you want the water to disperse away from the rest of the bathroom floor as soon as possible. Speak to your tiler about the correct fall of tiles so water is directed away from the rest of bathroom floor. They may give you a preference for efficiency. 900mm wall including small glass screen is not long enough for a walk in shower. You need at least 1200mm to stop water spray. As suggested by @Kate, install a 900mm long glass pivoted screen from the wall of shower. But you will still have water on the floor if your tiler does not do the new slope of tiles correctly for water to run directly to drain. 1200mm vanity would be fine for space. The width of the cabinet above vanity is your choice. How much “stuff” will be stored in cabinet?