Two simple words would resolve the issue in one fell swoop.
Unallocated seating.
We are (nearly) all adults, and with unallocated seats, people would very simply sort themselves out.
.........is the simple answer - stand/sit with your mates/family, front/back or whatever you prefer. Only issue, though, will be the usual few who stay on the concourse getting bladdered until half a millisecond before kick-off and pile into the stand en masse expecting to all be together, and then start pushing in front of everyone else, squeezing into already-packed rows etc