Tiny bathrooms are the hardest to design and get right. Your zig-zag wall between the two new bathrooms is going to make them both feel too pokey and small. Check the dimensions of your vanity as it looks too small, best to source what you would like to use, and draw it in to scale. Think about sightlines and resale without a bath. Consider how impractical outward opening doors are to rooms, especially if they affect circulation.

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Think outside the square and consider a diagonal dividing wall between the two, which will help make both spaces seem bigger.

Having two tiny bathrooms that feel claustrophic and are tiny to use won't be worth spending the money on. Depending on the type of construction and what is below the floor you could easily spend $30 or much more on this project. The only way to design a tiny bathroom is to draw up the plan and elevations at a large 1:20 scale to ensure that everything fits.

It is a tough one to solve nicely, so I would engage a professional designer to create a solution that will add value to your home. Your current proposal could possibly devalue it.

Best of luck,

Dr Retro of Dr Retro House Calls and Dr Retro Virtual Visits

Regarding council approval. Depending which state your in and then which council, as requirements may be different.
So contact YOUR council to get those answers.
Regarding cost. This can vary considerably as well. It depends on what the home walls and floors are made of and what specification you are expecting. Research with tilers, bathroom supply companies, and plumbers.

Option

Thanks Nice suggestion with minimum changes.

Is that ok?