Approximate ELO

There is a way to make an "absolute" rating in ELO, using an anchor competitor.

Choose one competitor, preferably a competitor which is never re-submitted, and define arbitrarily which rating it has. Then, modify rating updates so this anchor competitor rating never changes. All other competitors ratings will adjust in relation to the anchor competitor, instead of in relation to newer competitors added to the ranking.

I saw it been done in CGOS ranking.

But simply centering everyone around 1600 (ELO) or 50% (APS) is good enough for me.