Ideal situation for me would be combination of ESPHome’s bluetooth proxy functionality and Bluetooth speakers/headphones.
So Have ESP32s in many rooms, that talk over wifi with ESPHome / Home Assistant backend and connect over Bluetooth with Bluetooth speakers / headphones in the respective rooms. Basically ESPHome should support A2DP Bluetooth profile on ESP32.
Obviously they (The ESP32s instead of the Bluetooth speakers/headphones I’d assume would make more sense) should be seen as mediaplayers in Hass.
Also discussed here: ESP32 with Bluetooth Speaker as Media Player for Music Assistant - #13 by tipouletdomo
I created an ESPHome feature request, so please upvote 
Support for A2DP Bluetooth profile (mainly audio sender) · Issue #2456 · esphome/feature-requests · GitHub