Multiple sync accounts

[n4nn31355]

Would be nice to have able to use multiple sync accounts.

For example:
I want to sync bookmarks across all browsers. But I want my extensions and settings to sync only between Zen instances, and keep vanilla Firefox settings separate.

At this point, I either have bookmarks synced but no backup of the settings or the ability to use the same settings on another machine, or I don't have bookmarks synced.