Hi Thomas, containerizing both the solids and the pipelines are absolutely possible. Every dagster pipeline is always run in its own process, and you can use repositories to have different pipelines that use completely different python environments within the same Dagster deployment. There are also several ways to run each solid in its own container/process, depending on where you're deploying Dagster (e.g. in Kubernetes or not).
One thing we don't support yet is running different solids within a single pipeline in different images/python environments yet, but we're doing some work now with the goal of enabling that.