The majority of Thomas toys are bought by parents whose kids don't have many already and might not even be largely into Thomas. 16 is an adequate for a child that has a few, and if you were going to a friend's house or on holiday as a child, you'd bring a portable set or your little Collector's Playwheel instead of your whole collection. If a case with 84 spaces was released to the general public, then there would be this expectation that the child is going to get one of every single engine to put in all the spaces, which to me is quite unlikely. According to Fisher-Price, children have 20 Thomas vehicles on average.
In the future, I could see a slightly larger storage case being made in the shape of Thomas which could hold around 30 engines, and it could have a little play scene when opened up.
In the future, I could see a slightly larger storage case being made in the shape of Thomas which could hold around 30 engines, and it could have a little play scene when opened up.