HDB toilet renovation for open concept hotel style bathroom

Wow this open concept is kinda "too open" haha, well unless you are a young couple 😂 Maybe the glass here can be frosted, or there are some external curtains to be add-on. Trust me you don't want to be that "open" when you have big businesses going on inside..

Yes, you should at least try to add some of these blinds. Can adjust to your required openness as desired.

Back to your original question, I remember reading somewhere that for BTO you are not allowed to replace or hack your walls and floors of your bathroom for the first three years. The reason for this is that the waterproofing membrane installed by HDB needs time to stabilise, so water leakage doesn't occur.

Might need further confirmation for the above.

It definitely can be done! Been to a friend's newly renovated 4br today and thats exactly that they did. The walls between the master bedroom and the bathroom was hacked. Because of this they manage to fit a pretty decent size oval bathtub too! But do note that if you are taking hot showers often, the room can get humid if you do not have a decent appliance for dehumidifying.