Allow group based channel sharing - e.g. everyone

I've always wondered about having a tenant-wide "get in touch" channel for our team, so that colleagues outside our team can chat with the team directly without having to get membership/invited. It seems silly that teams aren't encouraged to talk to each other.

This could be achieved by creating a shared channel, and sharing it with the "everyone" group (or another group / team). This would then appear in everyone's teams/channel list without needing to follow an invite process. Having to add members individually to each tenant-wide channel is just too much administrative overhead. Having a user-badge to identify "official" in-team members in a conversation would be useful (although most people know each other).

Is there any way of doing this, or is this simply not possible?