Setting aside safety for a moment, consider just hygiene: BART is shockingly dirty. Which suggests mismanagement, above and beyond just a lack of detterence of criminality.
As for safety -- firing squads are probably not in the cards, but would jailing the violent be too much to hope for?
Riding without a ticket? Jail.
Littering on the platform? Straight to jail, right away!
Doing any violent crime in NK transit? Believe it or not - death by firing squad.
Here is a quick overview of how the system works: https://youtu.be/eiyfwZVAzGw?si=CnOMa8F6NkiyhifE