Can’t the President choose any person to represent him to another country? I don’t recall the Constitutional restriction that ambassadors must be appointed in a certain manner, and approved of by certain people. Henry Kissinger represented many Presidents without an official title.
Any time the media leads with a title, they are trying to inflate a balloon.
The president is in charge and not William Taylor.
If William Taylor does not like he could have resigned. Instead he is a member of the coup.
Presidents have used personal unofficial emissaries outside the State Department for decades.
Probably the best know was Harry Hopkins who Democrat Fascist Party god FDR used to do all sort of personal diplomacy.