You can still access it using a new flash with a trial install, it's just kind of a pain compared to a local backup.
I'm pretty sure I laid out a backup and recovery scheme already somewhere to automatically accomplish a way to do that, but here goes.
1. Assume every unraid install has a disk1 with at least 16GB free
2. After every successful boot, back up the flash drive to the root of disk1, compressed tar. Keep at least 2 copies, user configurable and dated.
3. New trial installs automatically attempt to read only mount all attached disks and look for valid tar backups. If found ask permission to recover using the backup of choice. Automatically change array auto start to false.
Various warnings and such about restoring backups after hardware changes, etc.
CA backup could easily be configured to do the backup part, the automatic recovery is a little harder.
@Squid, how hard is it to install plugins on a trial install? I've never tried, can you install CA and other plugins without an array defined?