Toss https://aws.amazon.com/ecs/anywhere on your own hardware and let someone else wake up at odd hours to worry about the container images making it on to the host.
This tool covers our use cases so far, and is easy to reason about. Ergonomically, it's very similar to Capistrano, which we're all familiar with.
It wasn't too bad to setup GitHub actions -> AWS ECR -> AWS CodeDeploy -> AWS ECS -> On-prem hosts via ECS Anywhere and that's worked well.
They didn't say that they're replacing their k8s setup for Hey explicitly, but they go on to say the reason they wrote MRSK is that they like the advantages of containers while getting lower complexity and being able to use their bare metal hardware. It seems like they want to go in that direction.