12×6' is a very very narrow space. your shower is going to need to all the way in the back. 5x5 foot for a roll in shower is ada. I use a wheelchair and I have a 10 1/2×12 1/2' bathroom. honestly, it's much too narrow. I would consider modifying my layout and stealing real estate from another area.

A floor plan would be a good start.

Thanks a lot for your comment. I wouldn't exactly call it a walk in-closet. As you can see from the drawing, Its space provided for two single wardrobe (one on each side). Maximum width can be around 3.5 ft. The humidity point is quite relevant. The question is would it be possible to include a wet room in the space i.e. 6ft x 8.6ft. - considering I don't remove the dress wall. Wanted to get a sense on the possible layout. Thanks and look forward to your advise.

I agree the plumbing looks sketchy i wouldn't invest a lot of money of decorative treatments if the pipes burst down the road. I would also look into your water quality it looks like you have a lot of rust stains that indicates high iron in your water which can really be hard on your plumbing and appliances. CLR is a product to improve the appearance but i would also look into Water softer as well. Stay away from natural products if your water is high iron they will stain fastest. Congratulations on the baby.