libsoundtouch has been significantly improved between the version hass is currently using (0.7.2) and the latest version on github (0.8.0):
https://github.com/CharlesBlonde/libsoundtouch
Bose’s Soundtouch API has also been improved since version 0.8.0 with asynchronous api calls:
https://developer.bose.com/guides/bose-soundtouch-api/bose-soundtouch-api-reference
Update: see this great post on an initial effort for this feature request: Bose Soundtouch - Source selection & presets