I know that aesthetically that the "plaza" looks COOL. What would be the in-universe explanation for this "plaza"? I am not being facetious here; I am attempting to understand this ship.
I guess it's purpose is likely to impress people who haven't seen that type of structure on a starship before. Remember, in the first film, Pike called the Enterprise
"our newest flagship".
So in-universe and out, its' function is to look "COOL".