We're building 4x3.5 Two with ensuite and the others with a jack and Jill. Life has changed unfortunately and now everyone in the household works, kids stay at home longer and ageing parents sometimes move in for care. At the moment we have a 3 x 1 and really the only thing we really want for is a second toilet, which growing up we had because we had the one out the back with the red backs.

depending on the size of the existing vanity it should be possible to have a similar new vanity or a custom unit made to replace the original but a chat with a plumber should be arranged to recommend suitable options and plan a schedule to remove the old and install the new, including any necessary waterproofing or tile repairs..btw careful removal could allow the original sink, taps and even the counter to be saved and recycled into a new vanity that matches the bathroom perfectly with the added option of being able to add different doors or drawers to the cabinet

depending on the size of the room and accurate location of existing doors and windows everything is out of proportion and all the concepts are hard to understand because we don't know the correct sizes ... the baths only look about 1200mm long, or the showers are oversized compared to the other fittings and look too small for a standard towel and what is the size of the storage and what can be stored in it....you need to collect a examples of proper sized fixtures eg a bath could be from about 1500 to 1800 long and 750 wide plus enough space to clean around a freestanding bath, most toilets need about 800 x 800 space to allow for elbow and knee room but there's lots of different sized toilets for different situations, showers need to be about 900 deep and say 900 to 1800 long but depends on available space and do you want a walk in shower with or without a glass screen or a shower cubicle or wet room or Japanese style ...dimensions are easily found on any manufaturers websites but allways start with accurate dimensions of the existing space and try again

i would probably try for at least 90cm but depends on the size and shape of the room, location of doors and windows and size and shape of other fixtures..can you post a plan of the room?