I have always wondered why it is not a service standard to walk through the F cabin (at least, J would be nice too) with a bottle of cold champagne on a tray topping up customers without them having to ask.
It is a very simple thing but would be extremely convivial and is definitely premium feeling. The very odd occasion it has happened proactively as the OP mentions above, it has been a nice touch.

I'm afraid it is exactly as CIHY fears, my expectations have been raised!