IMO, and take this for what it's worth, you should pick an ecosystem that works best for what you're trying to accomplish and completely build it out rather than trying to fit a round peg into the square hole. Getting these unrelated ecosystems to work effectively in tandem is nearly impossible.
I tried just about every one of the methods you're exploring here to do almost exactly what you're trying to do, and each of them had massive problems that rendered the method unworkable. You get into "I'm going to run this system with this plugin to accomplish goal a, and then feed into to the system that accomplishes goal b which has its own plugin for the next system down the line that accomplishes goal c," and you have too many possible points of failure and too many hacked together solutions to ever just sit back and listen to music.
I began to lose sight of the fact that the goal was to sit down, relax and listen to music, not run 24 hour tech support on my music listening system. You seem to be veering into "spending more time managing my system than enjoying my system" territory.
Once I realized that there is no one system that is going to tick all of the boxes, I took stock of what is important to me to get the most out of my music listening, and built it based on MusicBee, which was best at what I wanted to do. When I want to Chromecast or listen outside the house, I have my listening library synched to my android device because it is what works best for those things, then I have that android device report back the plays to MusicBee.
That's my example. phred's example is the most workable one for what he wants to do. Each of our systems relies on two systems that are not connected but report information to the other as needed.