We use components in apt.wikimedia.org to have different versions of packages that are only installed in select places.
My specific use case is that Shellbox will need a newer python3-pygments package from https://apt-browser.toolforge.org/buster-wikimedia/component/pygments/
In puppet we have apt::package_from_component https://gerrit.wikimedia.org/g/operations/puppet/+/7eabcbed220b880f17c25c42a49663065d0a6a66/modules/apt/manifests/package_from_component.pp
Mostly blubber just needs to add the sources.list entry for the component.
It would also be nice if it let you set a custom apt priority and created the correct pin file (like puppet does), but I don't have a usecase for that yet.