They should do what they do here in Europe. Set aside a particular section only for away fans (up in the nosebleeds, out of the way), which is segregated from the home crowd. Only sell tix for that area via the visiting teams.
Doesn’t solve the issue of home fans fighting amongst themselves but would put a stop to a lot of the shit that goes on right now.
If fans mixed in stadiums over here there would be full on, mass participation, riots every weekend. It would be carnage!!