For sure you can ID everyone. Nightclubs, music festivals and even airports do this sort of thing all the time.

You just need good organisation, plenty of security stations, and an atmosphere that rewards people who arrive early - checking a stadium's worth of IDs over the course of 2-3 hours rather than over the course of 20 minutes.

What you can't do is charge $20 for a glass of beer then expect people to arrive 2-3 hours before the game starts.