Adapting apartment to add a kid

We are currently living in the first picture floorplan with 3 kids. Everyone has their own room and life is easy. Now expecting 4th kid and need to rework things.

Ideas we have come up with:

1. give older kids the master. Divide it with a bung bed construction alike the second picture. Keep wardrobes as they are. Kids get the master bathroom. Probably by far the easiest and cheapest option as will require custom furniture, but no construction and wardrobes can stay as they are;

2. give older kids the master. Divide it into two actual rooms with an actual wall, although it will meet the window on one and and cannot be airproof (soundproof) due to the way the ventilation and AC have been set up. Rework the wardrobe so that the kid in the farther room will reach their room through the wardrobe and move the main door towards the window so that the master bathroom will become a shared area for the whole family.

Any further ideas or considerations are welcome.

As picture three I have added what our best/only alternative would be if we wanted to move to a 4BD, but stay in our area. The wall between kitchen and bedroom is currently not there so can move it up a bit (and would), but have not come up with any other ways to improve that floorplan.