Another possibility - What if full Asian non-astringent seeds were trialed in the thousands to just find pure Asian cold hardy genetics? I know Miss Kim is supposed to be able to survive in z6B already. Why not get started on seeds there? Is there something I’m missing?
https://tropicalfruitforum.com/index.php?PHPSESSID=bac5cfa9e5e6d3a660a4ba145e582653&topic=30891.0
This crazy person is growing citrus in Pennsylvania. If that can be done, why not persimmons?