2. Cal any international phone number using WebRTC directly from your browser.
If we talk about anything untraceable, can we even put in the same sentence "untraceable" and any "Google service"?. In this case WebRTC.
IMO phone call is too specific and personally it's not very interesting service. But if you were to offer virtual number (send/receive call and SMS) with good privacy policy, i would find it's interesting.
It's enough to receive only one SMS to activate Telegram acc, and voila.