Trying to solve this problem by adding even more goods to the market makes analysis unwieldy.
The addition of a composite good in a single-good model (bringing it up to two) allows for all other opportunities to be accounted for.
Since the composite is considered a single good only for purposes of the model, analysis can be made on a two-dimensional graph.
This final step clarifies the relation of the model to the real world where many goods can be stated in terms of money value.
In John R. Hicks's classic Value and Capital (1939), a composite good was used to generalize mathematically from consumer demand equilibrium for an individual in the 2-good case to market equilibrium via supply and demand in the n-good case.