its been pointed out on this thread already - a 60% rise in incidents outside the ground (if it was to go back to how it used to be). these incidents tend to be groups of away fans mouthing off, then groups of sunderland fans having a go back, and potentially some punches being thrown etc.. all in amongst a crowd of children, families and old people. those types of incidents is what i'm referring to. putting the away turnstiles bang in the middle of the busiest area of the outside of the stadium, where 80% of home fans walk past, is going to create aggro. aggro which doesn't exist now. so there, a problem created.
another problem, the seating arrangement inside. its not a problem now, we can sell 100% of the lower bowl to sunderland fans for any game we want, and hopefully for every game. put the away fans downstairs, and you have to block out 5000 seats for the away fans. you have to move potentially 5000 season ticket holders. every club that comes brings different amounts, so then you have empty blocks that we can't sell. there you go, another problem created that doesn't currently exist
then, at best, you put sunderland fans tight up against the away fans on both sides, and stuff gets thrown over, fans try to break through the stewards barrier, away fans end up on the pitch and potential clashes of fans in the stands and on the pitch (it happened when the fans were in the south stand) - something that can't possibly happen now - there you go, another problem created
then you have the cost and inconvenience of redesigning and reworking the concourse below, the seating, any fences that need putting up, segregation around the turnstiles etc.. we don't need any of that at the moment, so its not a problem. you move them downstairs, and there is another problem created
so, theres 4 problems off the top of my head that would be created by moving them downstairs, all of which don't exist currently.
we can solve the problem of the coventry fans throwing shit down without creating all of the above problems as a side effect