It’s a big project. I think it would be fun to get it all working, but it’s not all that clear-cut whether it will happen.
Some technologies could theoretically support this sort of mixing. Others can’t at all because of limitations outside of our control. Others could, but with some contortions involved.
The big question on our part is: if we do this, will it be stable? Will it be a good user experience? Will the synchronization quality actually be good? Will we be able to do effective QA on all of these mixed situations and make it actually useful for people?
Each of these technologies approaches the idea of synchronized playback differently. We’ll be trying to stretch across all of those differing approaches. Not simple stuff to make reliable.
Yeah, I know. It’s a little bit of work to support that. If we see enough demand, it will get done. I think this is the first time it’s come up (of course it’s only been a week 
). Not surprised that it came up in a Squeezebox context first.
This is a great solution that works today. For a long time I had an “airplay” speaker with something like this right behind it feeding the S/PDIF input. Worked perfectly and avoided the limitation.
See here: Is there room in Roon for an additional, "looser" synchronization flavor?