Is there any API available to modify the keyring? I understand from the Mailfence and Thunderbird partnership announcement that functionality like this will be added:
Thunderbird, will benefit from an automatic sync with all of the Mailfence tools: email, calendar, contacts, and encryption keys.
Currently, the Octopus implements a Parcimonie-like service. If a key has been superseded, Sequoia may find it (e.g., in WKD). Unfortunately, the user will only notice when they restart Thunderbird. Even if Thunderbird doesn't want to support the Octopus, Parcimonie-type of functionality could be added to RNP, and then something like this would be needed.
Finally, people are doing this anyway so it would be good to support them.