Authentication in TAXII

All,
There has been some discussion in Slack and on Github about relaxing the requirement for TAXII Servers to support Basic Authentication.
https://github.com/oasis-tcs/cti-taxii2/issues/58
What do people think of this?
If we decide to do this, we may need to look at adding some sort of optional property to the discovery resource, the API-Root resource, or some place else to let the client know what kind of authentication is supported.   What I would like to avoid is requiring the owner of a TAXII client from having to pick up the phone and calling the owner of the TAXII server to figure out what kind of authentication they use.
Bret