Lists of items with many value updates and rare changes of the list contents are suitable for what we call two-level push.

Unfortunately, the .NET client library offers no built-in support for two-level push, unlike other libraries. See the MultiDynaMetapush table in the web client library for instance. Would something similar fit into your case?
You could implement the same logic in your client. In this way, you could provide multiple items in COMMAND mode for different list compositions without redundancies: data for each single line would by provided by a common, dedicated item in MERGE mode.

On the other hand, unsubscribing and resubscribing to the whole group has some disadvantages.
It would be inefficient, because each row would be restarted with a new snapshot (and your table should manage to mask the discontinuity).
Moreover, you would still need asynchronous notifications that the group contents have changed, leading to something similar to the above mentioned "MultiMetapush" technique.