Headless core effort focuses on the generic use cases of the web automation. The effort is small, it prioritizes features aggressively and Widevine falls outside the scope. We are happy to review patches and help any feature to make its way into healdess for the sake of complete chrome / headless party.
For Widevine in particular, given that Headless provides virtual time, manual begin frame control and screen capturing capabilities, it feels like it goes directly against the Widevine spirit, so I'm not sure what exact scenarios media folks you refer to are after.
Also, headless can't have any dynamic components, it operates in the cloud in a predictable manner, so the code can't make outside connections and/or modify currently running version of the binary.
With that, I intend to close that bug as wontfix, but am open to the debate if you'd like to invite interested parties into this thread.
Regards