You can already use Bluetooth Proxy — ESPHome to forward data to Home Assistant (including BTHome, but also other BLE sensor integration data like Govee, Xiaomi-ble, etc.
Actually I am trying to use service to inject BTHome data to the BTHome integration.
My source is external source - you can treat it as a special proxy - over ESP-NOW using BTHome format without Bluetooth.
I would love to see a service to parse_data from external source - similarly as we had it in the passive_ble integration.