I was able to test another bluetooth stack, BlueSoleil. It does expose the HFP needed to use the Windows PC as a headset. Too bad it costs so much. Perhaps plugable could sell a licensed version of this stack with their dongle?
Thanks so much for the suggestion! There are a lot the various Bluetooth profiles can do. We include support for two stacks with our adapter: The Microsoft stack built-in to Windows (with a small broadcom HCI driver), and the full Broadcom stack (which can replace the Microsoft stack top to bottom).
See our FAQ at the bottom of http://plugable.com/products/usb-bt4le for the details on the Broadcom vs. the Microsoft stack on a per-profile basis.
Between the two of them, they cover much of the ground that’s possible with Bluetooth, but not all of it. We’re not planning on it at this point, and we haven’t tested BlueSoleil, but are always open to trying to offer bundles that provide some extra value.
Thanks again for the suggestion!