where will the toilet be?

in your proposal if the shower is at one end (a shower 1500 wide by 900 deep) and there's a vanity across the other end (1500 wide by 50 deep) there should be 1600mm between the shower and the vanity but where is your toilet?

Do you mean you are intending to have the ensuite with no toilet!?? That would be very unusual and highly impractical. But perhaps I have misunderstood?

Sorry I think removing the toilet is a mistake, you should be able to keep the same ensuite Layout, Glass shower screen only and a wall hung Vanity 900 x 450 or 800 x 450, Mirrored shaving style cabinets above, plus the toilet. Keep it very simple and it should look and feel much bigger, the wall hung vanity will make a big difference.

https://www.bunnings.com.au/forme-900mm-iron-ore-whitestone-wall-hung-cubo-basin-quay-vanity-unit_p4843558

They come with undermount basin as well

One of the space saving and for feel is to have no Nib walls it's not needed and in most cases not used in small ensuites. Hidden cistern's are great and quite expensive

my in wall cisterns with wall hung toilets were about $2000 including complex installation but they do make extra space and the one in the ensuite has the cistern built in under the extension to the vanity counter not the actual wall and the nib wall between the shower and the vanity is the perfect space for my fold down seat

Hi Lisa, I have a client with the exact ensuite layout. I have suggested leaving the plumbing where it is, replacing the vanity with wall hung, using large format tiles and mirrors to give the illusion of more space, and including low relief towel racks hung vertically (like a heated towel rail). It is squeezy for a couple but they don't need to use the ensuite at the same time. You may find having a separate toilet works for your lifestyle. It's a personal decision based on your lifestyle and whether you plan to move soon (in which case buyers may wish to have a toilet in the ensuite). Good luck. Cheers, Penelope

Certainly not as small as you'd think, a lot of ensuite's are smaller and still work quite well. I've done them as small as 2400 x 1250 with a cavity slider to the long wall. I believe that is about the limit for usability.

Use wall hung vanity and toilet as this will feel bigger. I don't think it would need to be bigger just aim for quality fit out rather than size.