A flag to enable/disable cloud sync on Fully-synchronized realms.
This would be convenient if you're offering sync as a premium feature.
Could something like this be achieved with the new flexible sync? If the queries don't sync the client data based on a parameter the client sets, then a fully synced realm wouldn't sync the local data for a non-premium user. Query-based sync seems to be the way forward to offer more flexibility for developers. Flexible sync may offer techniques already to at least limit sync for non-premium users.