I’m really curious as to how you guys are able to make the Audiophile edition of Band in a Box work directly off the hard drive with no need to download the program onto my Mac.
I don't think you can. The basic program is installed on the Mac (22GB in my case). Everything else (1.3TB) resides on the hard drive. You then point to the location of the tracks and VIs. Not quite intuitive but very easy once you understand the process.
Since my iMac doesn't have USB3, I moved everything over to an SSD that I access via eSATA. This is as fast as if it was internal. From there, it's the same deal as you open BIAB and point to the new location for the libraries and tracks. The 2018 tutorial videos should be a big help.
My next iMac will likely have USB-C—that will be plenty fast enough. I will still move the Audiophile libraries to an SSD, however.
I do hope that the next version can ship electronically, however. I have this collection of USB3 drives from PG Music and Native Instruments that I use once and put away. Even if it takes a day or two to download the entire package, I would prefer it to the way it ships now.