Support per-seat PipeWire instances
In Linux audio hardware gets assigned to the current foreground session in a seat, meaning that any session switching using Ctrl+Alt+F1 and similar will lose the audio if the session isn't running PipeWire. This can be annoying for audio that needs to stick to a seat and keep playing even without an active session, such as text-to-speech for screen readers.
Having a mode of some sort that would allow sharing a PipeWire session across a seat would help solve this as multiple users could play audio even when not in focus. Security policies would probably have to be applied here to allow only some apps to play or capture audio across sessions.