i didn't want to mix a race track theme, a nemo theme and a cowboy theme together in the same toy box creation.
a senior animator working on Disney Infinity was kind enough to answer a couple of questions that i asked. in case others had the same questions, i hope the answers clarify things.
q. can the items earned and put into the toy box be used to create multiple toy box worlds at the same time?
a. yes, every item earned can be used in multiple Toy Boxes
q. is it possible to have more than one toy box creation by the same player saved on a console?
a. yes, you can save multiple Toy Box creations on the same console
... time to do some more planning