With the release of WatchOS 7, it should now be possible for Spotify to add offline listening capabilities to the Spotify Apple Watch app (see Apple’s new AVFoundation: “Users can play locally-synced playlists or podcasts while on the go”). Please allow subscribers to download playlists to the watch itself so non-LTE watch owners can use the service solely with an Apple Watch and Bluetooth headphones.
Updated on 2020-09-25
A similar idea has also been suggested here, and only one thread can exist per idea:
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