Advice for sound design (assist/whole home audio)

We are building a home and “professional” automation systems are very expensive and they don’t even let you tinker with them. So I’ve been looking at Home Assistant so I can tinker and roll things out in stages. I’m not a fan of wireless, but I’m going to have to allow for lights and shades (still hardwired power). I think I have lights, shades, cameras and alarm system pretty well figured out and I’m stuck on the audio system. I want to hard wire as much as possible and run any cables I might want to use during the construction of the home.
I’ve done a lot of research on the topics, but can’t seem to get the correct terms for what I’m looking for. I don’t want to use Google or Amazon devices in every room for sound or Assist, I’d like speakers and a microphone (or 2 if needed) in the ceilings to have a “clean” look. I’d like to wire each room even though there would only be 6 or so rooms set up initially. I’d like to keep the Assist processing on-prem (looks like Willow is good for this). In order to meet the WAF (Wife acceptance factor), it’s going to have to be convenient to stream her music. I’d like for the doorbell to be played through the speakers (different volumes for different times of the day), Assist feedback, etc. Basically a big Google Alexa device, but specific to where the instructor is currently located.

Hardware ideas:

  • ETS SM1 Flush Mount Omni Directional Microphone
  • Monoprice 6-Zone Home Audio Multizone Controller and Amplifier
  • Tascam US-16x8 USB 2.0 Audio Interface

The idea is that the Monoprice would be controlled by HA to select the inputs and zone outputs for audio to be piped. The Tascam would be where the microphones would come in and the audio output of something like Music Assistant would be managed via USB. It appears that the Tascam will provide all 16 input channels as separate channels via USB. If that’s the case, then I’m unclear if Willow can listen to all 16 of those channels for the wake word and capture the command (the stuff I read seems to indicate that it can isolate the closest mic and use that), but I’m not sure if that’s only with the ESP32-S3-BOX units. It would be awesome if it sent channel information with the command so that if the command was “Alexa, raise the volume by 2.” then it would see that it was on channel X which HA maps to zone Y and just raises the volume on that zone without having to say “Alexa, raise the volume in the living room by 2.” when you are in the living room.
The other thing that I’m not clear on is “Chromecasting”. It sounds like you would connect YouTube Music account in something like Music Assistant and then control it that way rather than using your phone like you would control casting to a Google device. I’m guessing using the HA app on the phone could provide similar control of playlists and song selections. Can Music Assistant allow for 2 streams from YouTube Music to different zones (I’m guessing not) or would you need two accounts, etc? I don’t see a good way to have HA have general Chromecasting devices.
The goal is to not have screens and devices sitting on all kinds of surfaces and just be part of the home. Has anyone done something similar? Am I completely going the wrong way on this?

Thank you!