Firefox lets you save your logins to a CSV file. It would be nice, and I think an easy change, to be able to pipe the CSV file to a command. For instance, instead of a file name, you could type
| gpg -r RECIPIENT -e > FirefoxLogins.csv.gpg
This would avoid having the data in clear text on a file a user might forget to delete. This would have similar advantages when logins are restored or copied to a separate computer (e.g., one's laptop).