This is exactly how it should be done, and although many CO agents don't follow this process, quite a few do, and if they don't physically rope off the general lane, they decline to take customers from it during the preboard.

I think everyone is making this enhancement to be more of a pain than it is - done correctly, it truly improves the customer experience for those that matter more to the bottom line - Medallions, full Y and paid F. If you're personally against cutting in front of other customers, you're within your right to decline the Breezeway and wait in line, but don't suggest it should be taken away from everyone.

It's really simple -

1) rope off the GA lane
2) during boarding announcement remind ALL customers that the Breezeway is ONLY for customers seated in FC as well as Platinum, Gold, and Silver Medalions as well as Skyteam Elite and Elite Plus. All other customers MUST use the general lane and will not be boarded from the Breezeway. Breezeway eligible customers may board through their lane at any time during the boarding process and other passengers will give way to Breezeway customers during boarding.
3) call FC boarding through the Breezeway
4) call Zone 2/3 (mention Medallion, Skyteam by name) boarding through Breezeway
5) call Zone 4 (and so on) through the general lane, with a reminder during each subsequent announcement that Breezeway eligible customers should use their designated lane

It's a simple process and I can't for the life of me understand why agents are not following it accurately to a 'T' - and the lane is being handled worse over at NW where they've had over a year to get it right.