I think the core intention for the microphone to be able to answer calls is pretty useless since the eye wear does not have a audio source. In fact, it is quite useless if the intention of the microphone involves any audio feedback because if you need to put your phone in speaker mode, you don't need a microphone to begin with right?
Instead, I think if there is a mod that enables speech to text, it could help translate foreign language into text that you can view on your glasses. Other than this, I can't think of any usefulness of the microphone. The glasses could be better off without the feature or replace it with something else.