For me the main issue on trains is underagers spitting on trains, and then deliberately chucking stuff at people, spitting on people, screaming nonsense and trying to start fights with passengers.
Be better off clamping down on that, like you said it’s folk usually on their way home from a night out or afternoon sesh that cause the bother alcohol wise.
Not folk pre-drinking ok the train for football / hen night / stag do / going clubbing.