Conversion: Idea Generation and Feasibility

Here are a few pictures, as you can see, totally dangerous for children.

what we find beautiful is something like that, of that kind,

The nice thing is also expensive ;) You are right that there are "holes" at the areas where the stairs begin and end, which are dangerous for children. In the middle of the stairs it is OK. Since the stairs are winding, a simple "boarding up" doesn't work. Unfortunately, I don't have good suggestions, just the tip to go to the locksmith.