Possible to install a second gitlab of more recent version which uses another gitlab for git only?

We already have a gitlab EE on-premises, but it is managed by a central IT group, does git repo services only, and is over 2 versions old (12.10).
Is there some way we could set up our own gitlab install which would mirror or proxy those same git repos from the older central, while we used our own install for integrated CI and issue tracking?

Ideally it would follow the same project structure and share the same LDAP and SSO config, but those issues could probably be worked around.