Wow Metallicamaniac, that would be an awesome map - it's just the sort of thing I like to build too

I breifly considered making the Sydney Opera House, but with all the curved structures it would have proved too difficult, and no way to use occlusion efficiently either.
I would say the Norwegian Opera House is a much better prospect due to it being mostly flat sides and therefore easier to use occlusion to keep performance in the green and make the interior playable, but as Neg said using too much glass would push performance up towards the red, but you could leave the glass out completely though without it spoiling the looks - in fact the glass is so horrible and dirty, it would probably look better without it

Scale is always a problem with large structures - the bigger they are the easier they are to build and occlude but the more resources are used which push up the performance, smaller structures are less costly but more difficult due to the size of the pieces and also the use of occlusion.
If I was making that map, I would go with a larger (life size?) structure and try to keep the main building as simple as possible and use occlusion everywhere, so that the interior is playable - but that's just me

BTW, @DEEZ, I'm in agreement for the top three (or four?) maps for each comp. going into a final showdown - as you say it would give us all a chance to focus our map-making skills for the next new TOTM over at FCmaps.