Sorry here's the layout

You have a very large master bedroom but appear to have less generous ensuite. For size of master I would expect a 1500-1800 long vanity and space for towel rails plus 2 people. There is wasted space at entry to bedroom and the wir is at opposite end to ensuite so you have to take clothes to ensuite or walk back right across bedroom to wir I don’t like a partially open wir to bedroom and would close it up with doors. Your family toilet also Needs a basin.
There are lots of other layouts so hopefully others will post. I tried scaling your plan but was getting diff dimensions in each direction. Might be my iPad, but comment on what you like and don’t like with the options so we can try and get to a layout you prefer. You may like wir as you have it. You could also have frosted glass wall separating toilet from rest of bath to let light across. Or glass at top of toilet wall.

Thanks Katie for the suggestions. I hadn't thought about using frosted glass, which might be a good solution to let the light in. And yes will add a basin to the family toilet. The builder doesn't do cavity sliding doors - we're in Qld and I think the humidity has caused them too many issues. But it would be good to have the WIR closer to the bathroom.

Personally I would close up the access to wir making access from one end only with a swing door to maximise storage and minimise both visibility into ensuite and treat it as a seperate room helping to keep disturbance to bedroom at minimum if partner is still sleeping

A rough sketch of alternative layout.

My daughter put a Velux skylight in their shower to let light in

this plan doesn't appear to have a front entry or laundry ..are they upstairs or down?? please share a plan of the other level

What is the ceiling height? A window higher than 1800 in your shower shouldn’t require waterproofing, so could possibly have a long and narrow window above.

Thanks for all the advice, this is what we've ended up with in the final plan.

Very good to see that you have kept the ensuite Toilet on the external wall for best light and ventilation.. What depth is the vanity, if you can reduce it to allow for a 1m walkway. plus if you moved the vanity across to back onto the WIR you would have a better longer space for the vanity.

Great. Plus the vanity in the main toilet doesn’t need to be as wide or deep. Build some shelving around it in the impacted bedroom to depth of robe.

Use half the pantry for the linen store and pop toilet in the linen area with a hand basin. Right that's better. now put robe where ensuite ins now and ensuite the other end so it can be a tad longer. then it should all fit ok. Cheers MK PS what is up stairs? you do not need the additional toilet in the middle of the social areas.