Update: The initial implementation for structured APT has now been merged as an optional feature (needs to be actively enabled): Fixes #35959 - Use structured APT for deb content by quba42 · Pull Request #11058 · Katello/katello · GitHub
This should land in Katello 4.15.
We have yet to write documentation on how to enable and use the feature.
In some future Katello version, enabling the feature will become mandatory (automatic during upgrade).