Looking ahead and thinking about air travel massively growing: Couldn't the immigration be done by sending a self made "live" cell phone picture of the physical passport's machine readable page? Authorities will be able to check if the passport is valid in their databases anyway. This would add the proof that you have the actual document with you. Fines could be added for people just trying to send stored pictures and similar and maybe some wireless RFID verification or similar could be included? Immigration could be done during the flight and before landing, people could be directed to manned booths in case of any questions in need to be answered.