That's the reason I went with Docker compose and official docker image to start things rapidly during the POC.

Looking at the Dockerfile, it seems a bit complex: https://github.com/timescale/timescaledb-docker/blob/master/Dockerfile

I think the official Postgres image w/o TimescaleDB is also running as root but in Keycloak APB, it was made running on OpenShift. I might be talking nonsense, but it might be a good thing to check it out if you haven't done it.
https://github.com/aerogearcatalog/keycloak-apb/blob/eb32fdf15eddf83ff3af90633acb52fde85eb8cc/roles/provision-keycloak-apb/defaults/main.yml#L6

If above doesn't work, my thinking is if we can go with option #3 and offer it to RHSCL guys to put into their collection.

Otherr than this, I don't have much input to give. Phil Brookes was helping me with something similar once. looping him in.