Connect calls if two people are attempting to call each other at the same time
Often I'll be in situations where I'm trying to call someone at the same time they're trying to call me.
Currently, the result is that they never see my incoming call because they are in the middle of the outbound call experience and vice versa. We usually have to just stop and IM about who is going to call who before we can actually get connected.
Instead, I'd suggest handling calls as a 2-person meeting. When I called a friend, a "meeting" would be created. Then if they tried to call me at the same time, they'd simply join the meeting.
This way, if anyone had trouble during the call and needed to reconnect - for example, what if I answered the call on my Windows 10 Mobile device, but want to switch to my Xbox One X when I get home, I could connect to the call from the new device (turning it into a 3-person meeting) then disconnect with my Mobile without interrupting the continuity of the call.