BMD is a nice size, but it's essentially the wrong way round because you don't build stadiums East-West (there are a few exceptions but not many).
Obviously North-South is doable, as all the plans leaked/shown so far have that orientation, but it
is tight (bearing in mind circulation is needed as well) and it probably has knock-on effects on a number of things. I think the small north stand in the plans shown a while ago was an early attempt at one compromise solution. Maybe a better one has been worked out since, but the fact such ideas were being drawn up says to me they're really pushing the limits of what the site can take.
I made this a while ago to show just how tight it is...
What's bigger, Bramley Moore Dock, or Emirates Stadium