Are there disadvantages to storing bread in a vacuum box?
Bread gets dried out and stale through retrogradation which requires moisture.  Your vacuum bags are not keeping the bread fresh because of the vacuum, they are keeping it fresh by providing a very tight seal that prevents the bread from absorbing moisture from the atmosphere.  A larger vacuum box would provide the same protection from moisture but it might dry the bread out since the moisture in the bread would easily evaporate at the lower pressure.  Also keep in mind that neither a vacuum bag nor a vacuum box will prevent mold from eventually growing on the bread.

The biggest competition to a vacuum bread box is the freezer that most people already have in their kitchen.  Frozen bread can go for many weeks or even months without going stale and without any mold growing on it.  The only real risk to the bread is freezer burn if it is not sealed tightly.  Use vacuum bags to seal your bread tight and it can last a very long time in your freezer.