Doubling guests has nothing to do with technological restrictions. Heck, if we wanted we could have 5 to 10 guests.
I talked about this with Aludane. The issue is the show format isn't designed for two people. Its designed to profile and highlight one person.
The moment you introduce a second person, you water down the intimacy with either guest. People will act differently if they bring a buddy along for support.
It is also an additional preparation nightmare having to find an intersection between 4 respective timezones, assuming the second guest is not near the first guest geographically.