The voice comms are handled easily with things like TeamSpeak or Discord. No reason for anyone to devote cycles to that since it’s already done well.
The true multiplayer things are what IPACS will have to implement or provide hooks for. JoinFS lets you do all of the multiplayer stuff you mention as well as fly your own plane in the same scenery area as the other players for formation, sightseeing tours, and group flights. But Aerofly would need to take the information about other planes and show them to you.
And it is a huge blast to do. I’ve done a number of group flights in other flight sims with simultaneous voice comms and it is very enjoyable as everyone slots in for landings, takeoffs, saddles up in multi-ship formations, etc.
Sharing a cockpit in VR is really strange though. If you aren’t the one flying the plane, there can be a greater chance to feel motion sickness especially if the other pilot isn’t smooth. But it’s also really spooky. You just have to try it and see.