Hmm, there are probably other uses for containers with shrunken insides.
Inflatable mattresses (or waterbeds) that can be filled quickly/​efficiently.
If rooms can be enchanted in this way (houses can certainly be bigger on the inside) then enchanting a long hallway in this way would allow people to walk longer distances in a short amount of time.
If the container is transparent, it could be used as a magnifying glass for things you placed inside.
Inflatable mattresses (or waterbeds) that can be filled quickly/​efficiently.
If rooms can be enchanted in this way (houses can certainly be bigger on the inside) then enchanting a long hallway in this way would allow people to walk longer distances in a short amount of time.
If the container is transparent, it could be used as a magnifying glass for things you placed inside.
Wizards already have shrinking charms for the first one, but well done.