What you’re proposing is illegal and with good reason. The fact that it’s private property is neither here nor there.
Really? What law does it break?
By purchasing a ticket you agree to the terms and conditions, once of which already is that you may be filmed and recorded (by TV companies for example).
I'm just suggesting more cameras and audio recording equipment. If you think that's a threat on your civil liberties, you are free to choose not to attend matches.
This measure would increase the capturing of unacceptable racist abuse and lead to bans (and re-education) for those who made them.