I'm 100% for the backup option. Huge number of requests for help involve recovering data lost. (many just after a Refresh) I'd suggest adding a Make Backup option and Offering it as an option before users commit to a refresh.
Firefox Account and syncing your information would be ideal. Except I find the various passwords Firefox asks for very confusing. There seem to be the password I use when I create my account, which is NOT the password for my mail account. OK no probl...