Agree with the fact that this needs to be addressed, I don't think we will see much in the way of change this season though. The problem with creating an outer ring would only mean people congregating further away from the crowd but agree with this idea. Depending on how serious city view this matter and it seems they do view it as a serious matter then this is what I would personally propose,
A full secured perimeter fence around the Etihad (which I think we have, with access gates) with 5 outer access points. This area would be where you are searched as other posts have suggested. Have a canopy area at Gate 11, Away car park, The walkway at the base of the bridge, one on the Orange Car Park and another on Joe Mercer Way. Under these canopies they can have an x-ray machine for bags and several searching areas etc. The tram stops would need a fence built to funnel any supporters arriving in this way, to be directed to the search area on Joe Mercer Way. As
@west didsblue said this would then allow people to move freely once inside the perimeter fence. This idea was taken from my recent visit to Disney. Ha. Either way though, there's no pleasing everyone. I turned up 45 mins before the match was due to start on Saturday and still queued at M1 for 5-10 mins.