It would be great if you could self host your own sync server for Firefox, so you don't need a Firefox Account.
It could either work by only allowing users to sync when connected to the LAN the self-hosted sync server is running on, or accessible anywhere by setting up port-forwarding.
This would give the following advantages over the current system:
This wouldn't be a replacement for the current system but should be provided as and additional option.
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It could also be an idea to create an "app" for Netgear's ReadyNas, allowing you to host Firefox Sync off a Nasbox
I seem to remember that this used to be possible when syncing was introduced. But is it possible that support for self hosting was removed?