Display custom information as tab in Deployments preview and summary

We would like to post "status updates" from pipelines to both pull requests and the deployment screen.

For a pull request, this could be something like how some metric is changed by the PR, or our infrastructure-as-code use case of calculating the diff with current running systems.
These status updates would hopefully be shown above the comments section, and would be updated on every pipeline run.
It would be sufficient if it could just capture the output of a specific step in the pipeline and post it verbatim.

For deployments, we'd like a similar mechanism that could replace/augument the diff screen shown before promoting a build.
We currently run a pipeline step between our deployments that calculates the changes that will be made by running the deploy, but this requires some back-and-forth between screens. Having a new tab alongside commits/issues/diffs would be perfect.