On the preventing fraud issue, my suggestion would be to require the passenger to validate their own tickets in a date-stamping machine on the platform as in much of Europe. You would need to install the machines but as they work unattended they would be cheaper than ticket barriers.
I agree the installation of ticket validation machines would help in preventing fraud. It would also allow carnet tickets to be validated and could allows companies to buy tickets in bulk for common journeys such as London Paddington to Reading.