As I don't think it'll be too long until we see increases in fare evasion, increases to physical assaults on guards / gateline staff and potentially seeing some stations being shut completely because of already ongoing problems that are separate from the strikes, since most people in the north will feel ripped off and quite literally taken for a ride.
One person is trying to crowdfund a passenger's revolt where passengers taking part will refuse to buy tickets and the crowdfunding will be used to fund any fines Northern try to impose. I believe they are trying to get solicitors on board.