What we need
We just need somewhere to produce a gigantic bucket of standard lego parts. Nothing unusual--just your ordinary smallish bricks that you lose a lot of and there is no problem with that. This allows kids to do what I did when I was younger and play with their siblings in trying to make things. True, most of mine were basically box-shaped, with anything theoretically interesting on the side of the box or inside it on platforms, but we don't have to put imagination limits on it. I always thought my brother was much better at it than I was, but I now know he just produced the designs from the box while I produced the box.