Name me one great stadium that has open glass corners?... the ones that get mentioned as having great atmosphere - Westfalenstadion, San Siro, Nou Camp, the current Anfield, even Old Trafford... all completely enclosed.
Anfield is enclosed at the moment as are the other stadiums you mentioned, but a 'cauldron ' don't think so, only for the odd C/L / big prem game.
Anfield at the moment is living on its past with its 'great atmosphere' reputation, its the fans that make the atmosphere special, can't see glass corners at the kop end making it any worse than it is at present for the majority of our games.
Sometimes we see brilliant atmospheres created at 'little' clubs in shitty grounds with gaping gaps in between all the stands, doesn't seem to hinder the crowd much, infact they're the sort of grounds some big teams fear going to because of the very nature of them.
Most prem clubs now have managed to fill in the corners of there stadiums, don't think it's improved the atmosphere of any of them. The likes of Fulham make just as just noise when it suits them, and that's what it's all down to in my opinion....' when it suits them'
When it suits the fans, and the occasion warrrants it ( us included ) most clubs can make there atmosphere as good as they want to. Everton this season claimed one of UEFA Cup nights rivalled our C/L ones, they could be right, I wasn't there, certainly Wenger reckons Goodison is more intimidating than Anfield, and that's got a church in the corner of their ground !