No. You can include Depot Software objects (MSI, RPMs, etc) but not other blpackages.
If it's something you'd like to see (I know others have asked for this), then I'd definitely submit an enhancement request. It would be nice to maybe be able to set up nested folders in a BLPackage to allow for some organizing. In the meantime, if you do want to deploy multiple pieces of software in the same job, you can do what Bill was suggesting, or string multiple deploy jobs together within a Batch Job.