The door into ensuite currently opens in (hinged on left). Im thinking we will need to use a cavity slider door (which means shifting the bedroom light switches!) This project is growing!

If you could make a pocket door instead of a slider , you could use that entryway space.

I think like you -- I wouldn't spend $10k to make new cabinets just to centre things . A couple of 'thinking out loud' thoughts -- is it worth adding another layer of wallboard -- I'm thinking ply rather than gib -- then tiling over it ? It may stiffen everything , and ply has less flex , and as you are tiling over it , the finish doesn't matter too much , and the fact it would add say 18mm to the wall depth would be hidden by the fact that its to be tiled anyway . You may have to add a 'wider' facing around the doorway so it hides the extra thickness , but relatively easy to do ? Or is it worth looking at changing to a solid door ? Yes , I know it cuts space a bit , but depending whats on , say , the left hand wall , it may work , and its another way of stiffening up the wall , although it would need a builder .

windows in master bedroom need to allow views and privacy and much as i would prefer bed on NE this keeps the bed in view towards and from family room so prefer bed on south wests wall and small sliding doors pushed towards north side of room with tall narrow window beside sliding door and highlight window for light with privacy and wall space for chest of drawers...acknowledging theta the pwdr doesn't have a window but my suggested arrangement uses less total space more efficiently and is better for older kids and long stay visiting parents (more people can use the various options at the same time) and a small ventilating skylight will exhaust and brighten the toilet and vanity area ...the wide door into the lounge can be a stacker or stable door so you need to investigate local options (and everything is expensive unless it does what you want...we always use solid core doors that can be ten times the price of a basic hollow core door but love them so we economise elsewhere) and barn door between entry and family would be OK as long as you like them and it doesn't compromise lounge doors but could look ok if both doors are the same style and different widths...and location of dishwasher is personal and if you have already been unhappy with sink in main kitchen then have it in the scullery...main advantage of my suggested kitchen location is that it's closer to the front and the family area and external doors and the pantry uses the central space that can be much better illuminated with another ventilating skylight instead of a tiny external window and noisy exhaust fan