the proof of travel has always been abused, and people will always find a way round it as the club aren't that arsed.
sending back the ticket stubs after each game in order to record them may deter people from passing on spares bought for credits.
picking random tickets up out there with passport is probably the best way to manage it, and not that difficult.
i know there's a lot of people who don't go 'in their own name' but it's almost impossible to with the current selling process.
may be one for the supporters committee to take up with the club