In all honesty this whole issue over crowds entering and exiting the site will have been finely modelled to the highest standards by experts before it even went to planning to be minutely examined once again by more experts in the field before being approved .
All eventualities will have been modelled up to and including any emergencies that may arise that require mass evacuation of the site.
Openings in the wall will have tested and scrutinised during this intensive procedure.
So you don’t need to worry your pretty head about anything, just turn up have a few beers and watch the match.
Leave the worrying to professionals who know what their talking about,