You can: by closing the tab.

Which is what I plan to do to any tab that plays sound I didn't ask for.

I would prefer preventing audio + video to start on a tab that is not selected.

That would also prevent using a web browser to run a music player in the background.

Note the phrase preventing to start. Already playing media would be unaffected.

+: Also the rule would be extended to include minimized browser even if the tab is selected.

What does that even mean? You can't stop at a single file or stream as that would most likely still break things. If you allow tabs that play sound to continue to play sound you could just run a small, short, silent sound file on page load and then do whatever you want for the life of the tab.

I think you could mitigate the 'play short/silent sound on page load'. Each tab would have a max volume limit. The limit can be increased automatically while the tab is open, but it must stay within some % of that limit when the tab is not open. The default limit would be 0. You can add some restraints on the length of sound too, like require a sound to play for at least a second before adopting its new volume for the tab.

Agreed. This is a good start though. It's features like this that makes the utilitarian in me nod in approval.