It would've been gargantuan. Take a look at these promotional pictures from a 1931 booklet entitled "The Cathedral in Our Time".

Birds-Eye view showing the old poor house




The site of the Cathedral


Compared to the Three Graces


The Victoria Building tower fits snugly into the entrance arch of the Cathedral.


The Battleship HMS Hood compared to the Cathedral


Liver Buildings in comparison


This one looks like it was imagined from the roof of the Adephi with Brownlow Hill in the foreground.


The only thing I can say about it is that it was meant to provide a direct link to the catholic medieval cathedral cities. Often the cathedral would dominate the city - it would be THE building dwarfing its surroundings and I think Lutyens design was an attempt to re-capture that.