One possible solution with OA-level technology would be to upload the entire biosphere. Take the most detailed recording possible, bury a whole bunch of crashcaches with fabs and use the industry and data to regrow after the event. A massive undertaking sure, but for a terragen civ it costs little more than time and inconvenience given that the processes of terraformation are largely automated (like everything else).
OA Wish list:
- DNI
- Internal medical system
- A dormbot, because domestic chores suck!