reluctant to lose the convenience of outside access to a toilet my suggestion sacrifices a little space off the lounge and bedroom to keep the extra toilet and use the original laundry space for a bigger ensuite with separate toilet and double vanities, the new extension makes a more spacious wiw with only standard doorway openings to the new rooms but the ideal outside door for the laundry will depend on the location of the drying area and you may decide that a western door or no outside door (and walk through the verandah?) could both add more counter space to the laundry and, much as i like the gable roof for the extension, it would be interesting to obtain a comparative quote for a simple skillion roof (and raked ceilings for the new laundry and wiw) that may save a lot of extra roof structure that doesn't add anything to the inside of the new rooms or streetscape and could be much cheaper..

One question i have with your design Oklouise is whether the sloped ceiling will look odd in bed 2? The house is an old queenslander and bed 2 was originally the lounge room, with two sets of french doors opening on to an enclosed veranda. We are opening up the front veranda but not the side one (because that would limit the floor space we have available to build in downstairs). The "reading/playroom" was kept separate to the bedroom because that space has a steep sloped ceiling and a set of french doors opening on to it so we thought it looked like a separate space. If we remove the french doors and knock down the wall, do you think the bedroom will feel strange? We would like to keep the set of french doors opening on to the verandah at the front of the room.

I also like oklouise plan. good insulation is the key. In your original posted plan, Maybe change where the beds are positioned in the room. I think there is some bad feng shui if your head is backing onto a toilet. Apart from the noise factor, every time the toilet is flushed.

This is my bedroom/ensuite set up. Overall our rectangle is 3960 x 8030. this concept with WIR first then ensuite may work. However your bedroom size may have to be reduced. The measurements of spaces are along the top of plan. Orientation would be the same as my plan, just entrance door/window position would change.