Sync functionality is incoherent and needs better user controls

[cyaugin]

At present it seems like Sync works by recording any browser config changes to the cloud and then propagating the cloud state to all client devices. The problem is that the user may not intend for changes made to one device to be reflected on all of them. The way Sync currently works, once you have saved your login, Sync changes are performed automatically in both directions, without input from the user or notification to the user, and in general there is a lack of clarity in communicating how Sync actually works. I propose the following changes to Sync and its UI within Firefox.

1. Saving a login to Sync (in Firefox) should be decoupled from enabling or disabling its activities. The user should be able to stay logged in but, separately, choose to disable automatic syncing.
2. Option to confirm any changes to be propagated to/from the Sync cloud. To avoid repeatedly asking to make the same change, such changes could be tracked with a timestamp and Sync should automatically ignore any change that has already been seen.
3. Ability to review and adjust content on the cloud. In the event that a change was inadvertently propagated to the cloud, the user should be able to see the changes being tracked by Sync and manually remove them if desired.
4. Option for manual control of Sync. If enabled, Sync never transmits configuration data until the user requests it to do so. The user will determine the direction of the Sync, i.e. whether they want the current device configuration to become the cloud state, or vice versa.
5. Prompt for confirmation when logging into Sync for the first time on a new device/installation. Regardless of their cloud-saved settings, Sync will ask one time if the user wishes to import their cloud config into the new installation. If the user says yes, then Sync will import the config from the cloud, including the settings for Sync. If the user says no, then Sync will either consider the existing cloud config to be stale as in #2, or switch to manual mode as in #4.

[IM2BZ4Stupidity]

While I am somewhat satisfied with the functionality of Sync, there is one exceedingly annoying failing in how it works.  When setting up a new device, or one that's recently been redone with a clean OS install (Windows, Linux, Mac, iOS, Android, Chrome, et al), on installing Firefox, and signing in to Sync, bookmarks and settings, as well as plugins, themes, and extensions are synced, as expected. 

However, while everything carries over, and the assorted add-ons are automatically installed, there is a massive hiccup.  All the settings, for all the add-ons, for all synced devices, are reset.  All of the customization done, like in NoScript, or Ghostery, are reset, on all devices.  Even the built-in themes get reset to the defaults set on the newly installed and added Firefox install. 

Adding a new instance of Firefox to a Sync account, should not completely obliterate what is likely hours of tweaking and configuring an existing install, on another device, with the blank slate of the new.  Either default to moving all these tweaks to the new, from the old, or don't touch the configurations of the old, with the new.