Write now each Subscription has its own sync queue. I guess it will be better if Subscription will be work on Client sync queue by two reasons:
resource / performance issues, if you have they a lot. I my project I have at least 30 - 50 at some screens. Most of the time this queues are do nothing. They only purpose is a sync mechanism.
code can be look much simpler and easy for support.
Write now each Subscription has its own sync queue. I guess it will be better if Subscription will be work on Client sync queue by two reasons: