Consider adding a "configuration file" abstraction
While it is nice to offer the ability to configure containerized services via Ansible (because it allows arbitrary customization, besides being necessary for non-containerized services), it is true that the best practice envisions service-specific Ansible roles as only being responsible for generating some configuration files, possibly using templates.
It is then worth considering, with the intent of "hiding" Ansible as much as possible unless strictly necessary, if we could add a "configuration file" abstraction to the float service metadata, which would set up configuration files on the filesystem using Ansible templates. This would cover a lot of use cases, which would then no longer require an associated trivial Ansible role for configuration.
One of the obvious downsides is that it makes for a lot of ugly YAML, but this can be partially mitigated by using includes (eventually splitting down service metadata to one-service-per-file or such).