Hi Chris,
All the best for 2013 and sorry for the late answer as I was away for Christmas.
You can use the custom mode and a Gmail search request to do what you want.
Then, Gmvault is limited by the Gmail search request engine as depending on how many sub-labels you have below business it can make a convoluted search request because you will have to list all sub labels.
Note that you could also split the work with several Gmvault "sync" commands targetting in the same Gmvault-db.
Below is an example on how to proceed. Let say that you have below business 3 labels: contract, todo and archive. Here is the kind of Gmvault settings you should use.
$>gmvault sync --type custom --gmail-req "in:business/contract OR in:business/todo OR in:business/archive"
mye...@gmail.com -d ./my-db-dir
Let me know if it worked for you.
Best Regards,
The Gmvault developer