Earlier quoted context omitted.
What I dream of implementing at work (once our infrastructure is more fully containerized) is an addition to the CI/CD pipeline where each Pull Request doesn't just kick off tests but also spins up a full staging environment of its own, just waiting for reviewers/designers/PMs a click away. If there were no resource constraints you'd get a separate one for each commit/push so you could compare UX from individual chan…
You don't have to wait until you migrate to containerized deploys. Last year my team started deploying our project to folders named after the branch and setup one apache rule to redirect all *.dev. subdomains to the correct folder. We call them virtual development environments, and they worked really well with our existing QA process.
This also sounds very specific (probably using apache+cgi?). It won't really work for most techs out there.