Incidentally, I don't think there are any plans to destroy the
mainline station - if they did, it would be an act of vandalism on a
par with knocking the Arch down in the first place, since it's not
only a brilliant piece of 1960s architecture but also the only
mainline terminus that Just Works Really Well. Some refurbishment is
on the cards, but the structure and key features are staying the same
(or at least were on the last reports I saw).
Its horrifically ugly. And its so badly designed that it naturally
attracts druggies and tramps around the front, making it one of the
least inviting stations to arrive at. And inside is hardly any better,
so devoid of architectural quality that there is little to describe it
except "large empty box with shops round the outside".