Hi there,
I have recently implemented Custom-Metircs and HPA to a K8 project. I used prometheus for TSD and Grafana as monitoring tool. I used Custom-Metrics to Autoscale my PODs based on SQS queue size, http requests, java heap size etc.
Along with this i have 3 years experience working with various DevOps tools and Cloud Technologies.
Lets discuss in details to map your requirement with my experience and figure out the roadmaps/milestones for you projects.