We have an "Airman-certification" tag, but with the new distinction of the old "Practical Test Standards" currently being phased out, and the new "Airman Certification Standards" which seem to be raising more than a few questions in the aviation community an "Airman-Certification-Standards" tag would seem to me as a good idea because now we really have three topics:
General certification questions about experience, training, and flight time totals to qualify and other such bureaucratically-based questions.
I don't think we need a tag specifically for the ACS:
The PTS previously defined the standards for airman certification by the FAA (or more accurately, how you were tested to ensure you met those standards).
The ACS replaces the PTS, so airman certification testing under the FAA's jurisdiction will adhere to the ACS.
airman-certification-standards as a tag is inherently meta: It requires another tag (FAA, EASA, etc.) to clarify precisely whose standards we're taking about. The fact that the FAA named their standard like they are the only group promulgating a standard notwithstanding, other countries/jurisdictions may in fact vary significantly from the FAA ACS.