Docker Compose has always been an awesome file format, built on top of an idiosyncratic orchestration engine that doesn't interoperate well with anything else.
Writing a spec is a good first step! If work is underway to make this a shared multi-service dev environment that works across Kubernetes, ECS, etc, that would be even better.
When I read the spec, there are ominous words about partial implementations. That makes me nervous. But I'm cautiously optimistic.