An example of a fair and proportionate way is a £50 PF on top of paying the fare evaded, via a proper process with statutory appeals.
In my view fare evasion is equivalent in terms of culpability and harm to (say) low value shop lifting. It’s therefore fair and proportionate that it’s classified as a minor criminal offence and treated similarly in terms of sentencing.
Fraud is indeed a more serious offence and remains available as an alternative for prosecution.
Id be interested to know if any surveys have been done - anecdotally I strongly suspect most passengers want to see more enforcement not less.