I was a victim of one of the latest firmware updates and lost my HELM device for almost a week while they trouble-shooted and then eventually gave up a shipped a replacement. I still was not able to successfully restore from a backup nor have I been able to re-import history due to Googles new access policies.
So my feature wish - Allow for an option where HELM would cache email sent to a helm.. email domain if the device is in a catastrophic failure case. They would basically assume the destination identity and hold the emails in an encrypted form that could be replayed to the devices once they come back online.
This might violate the principle of the HELM device but as a disaster option could be useful.