At the moment /pub is managed by foreman_proxy_content (https://github.com/theforeman/puppet-foreman_proxy_content/blob/master/manifests/pub_dir.pp), but with Ubuntu Autoinstall you need to host the ISO and the extracted ISO somewhere as it is much more content than you want to download every time. So it would be great to have /pub also on a Foreman installation without Katello by default, as you need to work around the installer purging additional Apache Httpd configuration by default.
Simply moving this to Foreman is very likely not a solution as it is also needed on content proxy and simply adding it to Foreman will result in a conflict when using Katello with the included content proxy, so it needs some design decisions.