That sounds good in theory, but you're making an assumption that people want to make a video call with you at any time during the day.

Example: you're at work and your phone rings. Do you prefer doing a quick chat and get back to work asap or showing your face and doing a nice conversation? Same thing goes when you're outside and possibly at home.

The only time when this is going to work is when two people have previously committed to do a video call.

Again, I'm making an assumption too, only time can tell.