Do you really think these things can be solved by surveillance? I doubt people like you are describing are deterred by that and I don’t think DHS will start hunting possible homeless beggars because they have recordings.

What actually increases safety and one of the reason public transport was / felt safer in the past is more personal. If there are train guards on the ride or platform managers at the station, they can actually intervene. No surveillance necessary. But that obviously requires way more public transport funding.