I still believe long distance touring on a modern small scooter is possible. They seem to have one major weak point, and that is the belt. Choose a quality scooter with a belt that can be fairly easily replaced beside the road, and the tools to do it with. Everything else should be almost completely reliable. There is nothing quite like that sinking feeling when you are cruising along in the middle of nowhere, and the engine starts to rev as the scooter slows down. Kind of like a flat tire when you have nothing to fix it with.
2002 Vulcan 750 (now being slowly reassembled) 2013 Royal Enfield B5
2001 XT225, 2009 Genuine Stella
1980 Puch moped