Garmin Wellness seems to be a separate API to Garmin Connect. This would allow syncing weight data from Garmin to Zwift. Given that Zwift already has a connection to the Garmin Connect API, I expect it shouldn’t be hard to also add the Garmin Wellness API.
E.g. Today’s Plan connects to Garmin Wellness to get weight data.
This would automatically add support for a much wider range of smart weight scales, pretty much all ANT+ weight scales.
This should also solve Support for Underarmor scale via Myfitnesspal or Garmin Connect?