I saw this on my relative place and done through wood, hence even kids are not allow to jammed or play on the top similar to your First photo, as you could see that not column to hold it. Also your ceiling need to be high enough and also not "too high" heat too, else I guess they will jump down or better sleep a ground.

To keep inmind you may need to put a aircorn instead of Fan due to the limitation of the high on the ceiling too.

Alternative your could check below WEB and check with them...it not cheap, the ladder itself already 3-4K
http://bronteattic.com.my/v2/