It already exists. There is both Truphone and Airalo that I’ve used and actually quite liked. Much easier than finding a store to buy a sim. You can literally j

It already exists. There is both Truphone and Airalo that I’ve used and actually quite liked. Much easier than finding a store to buy a sim. You can literally just activate it at the airport with WiFi. Also how I tested a domestic carrier before switching over, I didn’t have to order a sim and wait 10 days. This is a non-issue.