There exists a KB article that offers guidance on the requirements and limitations of stretch clusters (clusters whose control-plane nodes span multiple sites).
https://access.redhat.com/articles/3220991

While stretch clusters are not officially supported in the openshift documentation, that article should be reviewed for its validity and also to see if any of the contents would be suitable to add to the official openshift documentation. Perhaps as a new section where stretch clusters are not officially sanctioned but still have guidelines around the setup.