@skhandu I’ll answer a few of your questions and leave the rest for Alex and other community members.
1- There is a SmartApp called VLC Thing, it mimics Sonos abilities (mostly) if you combine it with some other apps you can do this, at first I was turned off by the extra steps but I’m really loving it. I use VLC Thing, VLC on MAC, Air Foil on Mac, Air Foil on Android Tablets and Phones. Here is the thread about VLC Thing
2 - I think this feature is in the works
3- I think this feature is in the works
4 - Not sure this is at all possible but you can easily link to your other dashboard from this dashboard
5 - This is a great idea, I was just thinking about something like this on HADashboard
6 (lastly) - If you create a homescreen shortcut this should work, there are apps out there that you can use too that are meant for Kiosks. There is also an app I use called Immersive Mode which gets rid of everything except the webpage itself.